Composite materials for cookware

ABSTRACT

Composite materials for cooking apparatuses which are produced by applying, to a substrate, a material comprising a fluorine-containing polymer having an excellent adhesive property to the substrate without necessitating complicated steps and are excellent in heat resistance, non-sticking property, stain-proofing property, water- and oil-repelling property, stain-removing property, chemical resistance, rust-preventing property, antibacterial property, resistance to energy ray and abrasion resistance. The composite materials for cooking apparatuses are produced by applying, to the substrate, the material comprising a fluorine-containing ethylenic polymer having functional group which is prepared by copolymerizing (a) 0.05 to 30% by mole of at least one of fluorine-containing ethylenic monomers having at least one functional group selected from the group consisting of hydroxyl, carboxyl, a carboxylic salt group, a carboxylic ester group and epoxy, and (b) 70 to 99.95% by mole of at least one of fluorine-containing ethylenic monomers having no functional group mentioned above.

The present invention relates to composite materials for cookingapparatuses which are produced by applying, to a substrate, afluorine-containing polymer excellent in heat resistance, non-stickingproperty, transparency (property for exhibiting clear surface pattern),stain-proofing property and water- and oil-repelling property andparticularly in adhesive property to the substrate.

PRIOR ART

With respect to cooking apparatuses represented by a griddle and a ricecooker, it is desired that cooking can be done at higher temperature forshortening of cooking time and to pursue good taste of cooked dishes.Also it is desired that stains such as oil and scorch can be easilyremoved so as to make cleaning of these apparatuses easy after thecooking. Further good property for exhibiting clear surface pattern isalso desired from the viewpoint of appearance thereof.

In order to meet such requirements, for the composite materials used forcooking apparatuses (cooking appliances, wares, utensils, tools, etc.),a fluorine-containing resin which is excellent in heat resistance,chemical resistance, weather resistance, surface properties (frictionresistance, etc.), electric insulating property and the like is used inthe form of coating or film.

However the fluorine-containing resin involves a substantial problem,namely insufficient adhesion to a metal or glass substrate due to itsexcellent non-sticking property.

Therefore in case where the fluorine-containing resin is used in theform of coating, there is a method of adhering a fluorine-containingresin to a substrate by roughening the surface of metal chemically orphysically with expecting anchor effect between them. However thismethod requires much labor in the surface roughening itself, and thoughinitial adhesion is possible, lowering of the anchor effect arises whena temperature change is made repeatedly and in case of use at hightemperature.

Also a method for chemically activating a surface of afluorine-containing resin by treating the surface with a solutionprepared by dissolving metallic sodium in liquid ammonia has beenproposed. However in that method, not only there is a fear that thesolution itself causes environmental pollution but also there is aproblem that its handling is attended with danger.

Further though a method for carrying out physical and chemical treatmentsuch as plasma sputtering on a surface of a fluorine-containing resinhas been proposed, there is a problem that much labor is required forthe treatment and an increase in cost is resulted.

Also in order to improve adhesion of a fluorine-containing resin coatingcomposition, investigations with respect to addition of variouscomponents and use of a primer have been made.

For example, there is a technique of adding an inorganic acid such aschromic acid to a coating composition containing a fluorine-containingresin to form chemical conversion coating film on a surface of metal forenhancing adhesion of the composition (JP-B-63-2675). However sincechromic acid contains hexahydric chromium, it cannot be said that such atechnique is sufficient in view of safety in food and coating work.Further in case of use of other inorganic acids such as phosphoric acid,there was a problem that safety of a fluorine-containing resin coatingcomposition is damaged.

Use of a coating composition containing a fluorine-containing resin as aprimer, in which heat resistant resins such as polyamideimide,polyimide, polyethersulfone and polyether ether ketone and in addition,a metal powder are added instead of the above-mentioned inorganic acid,has been studied (JP-A-6-264000). Inherently there is almost nocompatibility between a fluorine-containing resin and a heat resistantresin. Therefore there arises a phase separation in a coating film, thuseasily causing intercoat adhesion failure between the primer and the topcoat of the fluorine-containing resin. Further film defects such as pinholes and cracks arise easily at the time of processing at hightemperature or during use due to a difference in heat shrinkage betweenthe fluorine-containing resin and the heat resistant resin or due tolowering of elongation of the coating film by the addition of the heatresistant resin. Also since those heat resistant resins are coloredbrown by baking, property for exhibiting clear surface pattern is poorand it is difficult to use them for applications requiring white andvivid colors and transparency. Further when the heat resistant resin isblended, non-sticking property and friction resistance which thefluorine-containing resin possesses inherently are lowered.

Also for adhesion of a fluorine-containing resin coating composition toglass, etc. requiring transparency, an improvement of the adhesion hasbeen tried by treating the substrate with a silane coupling agent oradding a silicone resin to the fluorine-containing resin coatingcomposition (JP-B-54-42366, JP-A-5-177768). However enhancement ofadhesion is insufficient, heat resistance is lowered and separation offilm, foaming and coloring arise easily at sintering or in use at hightemperature.

On the contrary, fluorine-containing resin coating compositions preparedby copolymerizing a hydrocarbon monomer (containing no fluorine)containing functional group such as hydroxyl or carboxyl have beendiscussed. However those coating compositions were originally studiedmainly for a purpose of weather resistance, and it is difficult to usethem for application requiring heat resistance at 200° to 350° C. whichis directed by the present invention, and for applications requiringnon-sticking property, friction resistance, etc.

Namely with respect to a polymer prepared by copolymerizing ahydrocarbon monomer (containing no fluorine) having functional group,thermal decomposition easily occurs on components of the monomer at thetime of processing at high temperature or during use, and thus coatingfilm failure, coloring, foaming, separation, etc. arise, which makes itimpossible to attain purposes of coating a fluorine-containing resin.

Further fluorine-containing resins are generally insufficient inmechanical strength and dimensional stability, and high in price. Inorder to make the best use of the above-mentioned merits of thefluorine-containing polymer and minimize its disadvantages,investigations have been made also with respect to its use in the formof film.

However the fluorine-containing resin inherently has low adhesive force,and it is difficult to adhere the fluorine-containing resin directly toother material (substrate). For example, even if the adhering is triedby thermo-processing, adhesive strength of the fluorine-containing resinis not enough, or even if the resin has adhesive force to a certainextent, such an adhesive force is apt to vary depending on kind of thesubstrate. Thus in many cases, reliability on the adhesive strength ofthe fluorine-containing resin has been not so enough.

In order to adhere the fluorine-containing resin film to a substrate,mainly the following methods have been studied:

1. a method for physically roughening a surface of substrate by sandblasting, etc.,

2. a method for surface-treating a fluorine-containing resin film bychemical treatment such as sodium etching, plasma treatment,photochemical treatment, etc.,

3. a method for adhering by using an adhesive, and other methods. Withrespect to the methods 1 and 2 above, surface-treating steps arerequired, and the steps are complicated and productivity is poor. Alsokinds and shapes of substrates are restricted. The fluorine-containingresin film inherently has low adhesive force, and there easily occurproblems with appearance such as coloring and color (property forexhibiting clear surface pattern) of the obtained composite material.Also the method of using a chemical such as sodium etching has a problemwith safety.

Use of an adhesive in the method 3 above has also been discussed. Ausual hydrocarbon type (non-fluorine-containing) adhesive does not haveenough adhesive property and its heat resistance is insufficient. Thus ahydrocarbon type adhesive cannot stand under conditions for adhering ofa fluorine-containing polymer film, which requires molding andprocessing at high temperature, and peeling due to decomposition of theadhesive and coloring occur. The above-mentioned laminated articleproduced by using an adhesive also lacks in reliability with respect toits adhesive property, since an adhesive layer is insufficient in heatresistance, chemical resistance and water resistance and its adhesiveforce cannot be maintained due to a change in temperature andenvironment.

On the contrary, adhesion by using an adhesive and adhesive compositioncomprising a fluorine-containing polymer having functional group isdiscussed.

For example, it is reported that a fluorine-containing polymer preparedby graft-polymerizing, to the fluorine-containing polymer, a hydrocarbonmonomer which has carboxyl represented by maleic anhydride andvinyltrimethoxysilane, a residual group of carbonic acid, epoxy or ahydrolyzable silyl group, is used as an adhesive (for example,JP-A-7-18035, JP-A-7-25952, JP-A-7-25954, JP-A-7-173230, JP-A-7-173446,JP-A-7-173447) and that an adhesive composition comprising afluorine-containing copolymer prepared by copolymerizing a hydrocarbonmonomer having functional group such as hydroxyalkyl vinyl ether withtetrafluoroethylene or chlorotrifluoroethylene and an isocyanatehardening agent is cured and used as an adhesive between vinyl chlorideand corona-discharged ETFE (for example, JP-A-7-228848).

The above-mentioned adhesive or adhesive composition comprising afluorine-containing resin prepared by graft-polymerizing orcopolymerizing a hydrocarbon monomer having functional group does nothave enough heat resistance, and thus at the time of processing acomposite material comprising the adhesive or adhesive composition and afluorine-containing resin film at high temperature or during use at hightemperature, decomposition and foaming occur, thereby causing reductionof adhesive strength, peeling and coloring. In case of the adhesivecomposition disclosed in JP-A-7-228848, it is necessary tocorona-discharge the fluorine-containing resin film.

As mentioned above, there have been no material for composite materialsfor cooking apparatuses which meets the above-mentioned requirements andassures strong adhesion to a substrate and excellent property forexhibiting clear surface pattern.

In view of the above-mentioned facts, an object of the present inventionis to provide composite materials for cooking apparatuses which areproduced by applying, to a substrate, a material comprising afluorine-containing polymer being excellent in adhesion to the substratewithout necessitating complicated steps.

Further an object of the present invention is to provide compositematerials for cooking apparatuses which are excellent in non-stickingproperty, stain-proofing property, water- and oil-repelling property,stain removing property, chemical resistance, rust preventing property,antibacterial property, resistance to energy ray and frictionresistance.

DISCLOSURE OF THE INVENTION

The present invention relates to composite materials for cookingapparatuses which are produced by applying, to a substrate, a materialcomprising a fluorine-containing ethylenic polymer having functionalgroup and prepared by copolymerizing:

(a) 0.05 to 30% by mole of at least one of fluorine-containing ethylenicmonomers having at least one functional group selected from the groupconsisting of hydroxyl, carboxyl, a carboxylic salt group, a carboxylicester group and epoxy and

(b) 70 to 99.95% by mole of at least one of fluorine-containingethylenic monomers having no functional group mentioned above.

In that case, it is preferable that the above-mentionedfluorine-containing ethylenic monomer (a) having functional group is atleast one of fluorine-containing ethylenic monomers represented by theformula (1):

CX₂═CX¹—R_(f)—Y  (1)

wherein Y is —CH₂OH, —COOH, a carboxylic salt group, a carboxylic estergroup or epoxy, X and X¹ are the same or different and each is hydrogenatom or fluorine atom, R_(f) is a divalent alkylene group having 1 to 40carbon atoms, a fluorine-containing oxyalkylene group having 1 to 40carbon atoms, a fluorine-containing alkylene group having ether bond and1 to 40 carbon atoms or a fluorine-containing oxyalkylene group havingether bond and 1 to 40 carbon atoms.

Further it is preferable that the above-mentioned fluorine-containingethylenic monomer (b) having no functional group is tetrafluoroethylene.

Further it is preferable that the above-mentioned fluorine-containingethylenic monomer (b) having no functional group is a monomer mixture of85 to 99.7% by mole of tetrafluoroethylene and 0.3 to 15% by mole of amonomer represented by the formula (2):

CF₂═CF—R_(f) ¹  (2)

wherein R_(f) ¹ is CF₃ or OR_(f) ², in which R_(f) ² is a perfluoroalkylgroup having 1 to 5 carbon atoms.

Further it is preferable that the above-mentioned fluorine-containingethylenic monomer (b) having no functional group is a monomer mixturecomprising 40 to 80% by mole of tetrafluoroethylene, 20 to 60% by moleof ethylene and 0 to 15% by mole of other monomer copolymerizable withthose monomers.

Also the present invention relates to the composite materials forcooking apparatuses, which are produced by applying, to a substrate, theabove-mentioned fluorine-containing ethylenic polymer having functionalgroup in the form of coating.

Also the present invention relates to the composite materials forcooking apparatuses, which are produced by applying, to a substrate, theabove-mentioned fluorine-containing ethylenic polymer having functionalgroup in the form of an aqueous dispersion.

Also the present invention relates to the composite materials forcooking apparatuses, which are produced by applying, to a substrate, theabove-mentioned fluorine-containing ethylenic polymer having functionalgroup in the form of a powder coating composition.

Also the present invention relates to the composite materials forcooking apparatuses, which are produced by applying, to a substrate, theabove-mentioned fluorine-containing ethylenic polymer having functionalgroup in the form of a film.

It is preferable that the above-mentioned substrate is a metallicsubstrate.

Also it is preferable that the above-mentioned substrate is a glasssubstrate.

The present invention relates to cooking apparatuses produced by usingthe composite materials for cooking apparatuses.

Also the present invention relates to heating apparatuses for cookingproduced by using the composite materials for cooking apparatuses.

Also the present invention relates to a griddle produced by using thecomposite materials for cooking apparatuses.

Also the present invention relates to a griddle produced by using thecomposite materials for cooking apparatuses on its heating surface madeof metal.

Also the present invention relates to a griddle produced by using thecomposite materials for cooking apparatuses on its glass lid.

Also the present invention relates to a range with oven produced byusing the composite materials for cooking apparatuses.

Also the present invention relates to a range with oven produced byusing the composite materials for cooking apparatuses on its innersurface made of metal.

Also the present invention relates to a range with oven produced byusing the composite materials for cooking apparatuses on its cookingplate.

Also the present invention relates to a range with oven produced byusing the composite materials for cooking apparatuses on its glass door.

Also the present invention relates to a heating pot produced by usingthe composite materials for cooking apparatuses.

Also the present invention relates to a heating pot produced by usingthe composite materials for cooking apparatuses on its heating surfacemade of metal.

Also the present invention relates to a heating pot produced by usingthe composite materials for cooking apparatuses on its glass lid.

Also the present invention relates to a frying pan produced by using thecomposite materials for cooking apparatuses.

Also the present invention relates to a frying pan produced by using thecomposite materials for cooking apparatuses on its heating surface madeof metal.

Also the present invention relates to a fryer produced by using thecomposite materials for cooking apparatuses.

Also the present invention relates to a fryer produced by using thecomposite materials for cooking apparatuses on its inner surface made ofmetal.

Also the present invention relates to a fryer produced by using thecomposite materials for cooking apparatuses on its inner surface made ofglass.

Also the present invention relates to a rice cooker produced by usingthe composite materials for cooking apparatuses.

Also the present invention relates to a rice cooker produced by usingthe composite materials for cooking apparatuses on its inner surfacemade of metal.

Also the present invention relates to a rice cooker produced by usingthe composite materials for cooking apparatuses on its inner lid made ofmetal.

Also the present invention relates to a pot produced by using thecomposite materials for cooking apparatuses.

Also the present invention relates to a pot produced by using thecomposite materials for cooking apparatuses on its inner surface made ofmetal.

Also the present invention relates to a pot produced by using thecomposite materials for cooking apparatuses on its inner lid made ofmetal.

Also the present invention relates to a tableware or vessel produced byusing the composite materials for cooking apparatuses.

Also the present invention relates to a metallic tableware or vesselproduced by using the composite materials for cooking apparatuses.

Also the present invention relates to a glass tableware or vesselproduced by using the composite materials for cooking apparatuses.

Also the present invention relates to cooking apparatuses for processingfoods which are produced by using the composite materials for cookingapparatuses.

Also the present invention relates to cooking apparatuses for mixingfoods which are produced by using the composite materials for cookingapparatuses.

Also the present invention relates to cooking apparatuses for cuttingfoods which are produced by using the composite materials for cookingapparatuses.

Also the present invention relates to baking apparatuses produced byusing the composite materials for cooking apparatuses.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a diagrammatic plan view of an adhered sample made to measureadhesive strength in Example 7 of the present invention.

FIG. 2 is a diagrammatic perspective view of a test sample used tomeasure adhesive strength in Example 7 of the present invention.

FIG. 3 is a diagrammatic perspective view of a laminated article made toproduce a test piece to be subjected to adhesion test (T-type peelingtest) in the present invention.

FIG. 4 is a diagrammatic perspective view of a test piece to besubjected to adhesion test (T-type peeling test) in the presentinvention.

FIG. 5 is a diagrammatic perspective view of a test piece to besubjected to adhesion test (tensile shear strength test) in the presentinvention.

FIG. 6 is a diagrammatic view of a test device to be used for adhesiontest (tensile shear strength test) in the present invention.

FIG. 7 is a diagrammatic cross-sectional view of a laminated test platemade in Example 15 of the present invention.

FIG. 8 is a diagrammatic cross-sectional view of a three-layeredlaminated article made in Example 15 of the present invention.

FIG. 9 is a diagrammatic cross-sectional view of a laminated articlemade in Comparative Example 10 of the present invention.

FIG. 10 is a diagrammatic cross-sectional view of a laminated test platefor making a laminated article in Example 16 of the present invention.

FIG. 11 is a diagrammatic cross-sectional view of a laminated articlemade in Example 16 of the present invention.

FIG. 12 is a diagrammatic cross-sectional view of a laminated article tobe subjected to T-type peeling test in Example 16 of the presentinvention.

FIG. 13 is a diagrammatic cross-sectional view of a laminated article tobe subjected to T-type peeling test in Comparative Example 10 of thepresent invention.

FIG. 14 is a diagrammatic cross-sectional view of a laminated test platemade in Comparative Example 12 of the present invention.

FIG. 15 is a diagrammatic perspective view of a test piece to besubjected to non-stickiness test in Example of the present invention.

FIG. 16 is a diagrammatic perspective view of an aluminum plate having acoating film and obtained in (1) of Example 19 of the present invention.

FIG. 17 is a diagrammatic perspective view of a test sample formeasuring adhesive strength in (2) of Example 19 of the presentinvention.

FIG. 18 is a diagrammatic cross-sectional view of a laminated test platemade in Example 22.

FIG. 19 is a diagrammatic cross-sectional view of a three-layeredlaminated article made in Example 22 of the present invention.

BEST MODE FOR CARRYING OUT THE INVENTION

The composite material for cooking apparatuses of the present inventionis one produced by applying, to a substrate, a material comprising afluorine-containing ethylenic polymer having functional group andprepared by copolymerizing:

(a) 0.05 to 30% by mole of at least one of fluorine-containing ethylenicmonomers having at least one functional group selected from the groupconsisting of hydroxyl, carboxyl, a carboxylic salt group, a carboxylicester group and epoxy and

(b) 70 to 99.95% by mole of at least one of fluorine-containingethylenic monomers having no functional group mentioned above.

The above-mentioned material comprising a fluorine-containing ethylenicpolymer having functional group has surprisingly strong adhesiveproperty in the form of coating or film to metal, glass and othersubstrates even without use of an adhesive, surface-treatment on thesubstrate, formation of a primer layer and addition of a componenthaving adhesive property in the material.

With respect to the fluorine-containing ethylenic polymer havingfunctional group which is used for preparing the composite material ofthe present invention, it is important to copolymerize (a) theabove-mentioned fluorine-containing ethylenic monomer having functionalgroup and (b) the fluorine-containing ethylenic monomers having nofunctional group mentioned above to introduce the functional group intothe fluorine-containing polymer, thereby making it possible to giveexcellent adhesive force directly to surfaces of various substrates, towhich adhesion has been difficult or impossible. Namely as compared witha fluorine-containing polymer prepared by copolymerizing anon-fluorine-containing monomer having functional group, thefluorine-containing polymer of the present invention is excellent inheat resistance, and decomposition at processing at high temperature(for example, 200° to 400° C.) can be inhibited more and a largeadhesive strength can be obtained. Further a coating layer being freefrom coloring, foaming, pin hole caused thereby and leveling failure canbe formed on a substrate. Also in case where the composite material isused at high temperature, adhesive property is maintained and a coatinglayer failure such as coloring, whitening, foaming or pin hole isdifficult to arise.

The above-mentioned fluorine-containing polymer having functional grouphas excellent characteristics such as not only heat resistance thereofbut also chemical resistance, non-sticking property, stain-proofingproperty, friction resistance and weather resistance of afluorine-containing polymer and can give such excellent characteristicsto a composite material without lowering them.

Then the fluorine-containing ethylenic copolymer having functional groupwhich is a material for the composite material of the present inventionis explained below.

The functional group of the fluorine-containing ethylenic polymer havingfunctional group is at least one functional group selected from thegroup consisting of hydroxyl, carboxyl, a carboxylic salt group, acarboxylic ester group and epoxy, and provides the polymer with adhesionto various substrates by its effect. Kinds and combination of thefunctional groups are optionally selected depending on kind of a surfaceof the substrate and purpose and application. From the viewpoint of heatresistance, hydroxyl is most preferable.

Examples of the preferred fluorine-containing ethylenic monomer (a)having functional group which is one of components constituting thefluorine-containing ethylenic polymer having functional group arefluorine-containing ethylenic monomers (a-1) having functional groupwhich are represented by the formula (1):

CX₂═CX¹—R_(f)—Y  (1)

wherein Y is —CH₂OH, —COOH, a carboxylic salt group, a carboxylic estergroup or epoxy, X and X¹ are the same or different and each is hydrogenatom or fluorine atom, R_(f) is a divalent alkylene group having 1 to 40carbon atoms, a fluorine-containing oxyalkylene group having 1 to 40carbon atoms, a fluorine-containing alkylene group having ether bond and1 to 40 carbon atoms or a fluorine-containing oxyalkylene group havingether bond and 1 to 40 carbon atoms.

Examples of the fluorine-containing ethylenic monomer (a-1) havingfunctional group are one represented by the formula (3):

CF₂═CF—R_(f)—Y  (3)

wherein Y is as defined in the above formula (1), R_(f) ³ is a divalentfluorine-containing alkylene group having 1 to 40 carbon atoms or OR_(f)⁴, in which R_(f) ⁴ is a divalent fluorine-containing alkylene grouphaving 1 to 40 carbon atoms or a divalent fluorine-containing alkylenegroup having ether bond and 1 to 40 carbon atoms, one represented by theformula (4):

CF₂═CFCF₂—OR_(f) ⁵—Y  (4)

wherein Y is as defined in the above formula (1), R_(f) ⁵ is a divalentfluorine-containing alkylene group having 1 to 39 carbon atoms or adivalent fluorine-containing alkylene group having ether bond and 1 to39 carbon atoms, one represented by the formula (5):

CH₂═CFCF₂—R_(f) ⁶—Y  (5)

wherein Y is as defined in the above formula (1), R_(f) ⁶ is a divalentfluorine-containing alkylene group having 1 to 39 carbon atoms or OR_(f)⁷, in which R_(f) ⁷ is divalent fluorine-containing alkylene grouphaving 1 to 39 carbon atoms or a divalent fluorine-containing alkylenegroup having ether bond and 1 to 39 carbon atoms, one represented by theformula (6):

CH₂═CH—R_(f) ⁸—Y  (6)

wherein Y is as defined in the above formula (1), R_(f) ⁸ is a divalentfluorine-containing alkylene group having 1 to 40 carbon atoms, or thelike monomer.

From the viewpoint that copolymerizability with the fluorine-containingethylenic monomer (b) having no functional group is comparatively goodand that heat resistance of the obtained polymer is not loweredremarkably, the fluorine-containing ethylenic monomers having functionalgroup and represented by the formulae (3) to (6) are preferable.

Among them, from the viewpoint of copolymerizability with thefluorine-containing ethylenic monomer (b) having no functional group andheat resistance of the obtained polymer, the compounds of the formulae(3) and (5) are preferable, and the compound of the formula (5) isparticularly preferable.

Examples of the fluorine-containing ethylenic monomer having functionalgroup and represented by the formula (3) are:

CF₂═CFOCF₂CF₂CH₂OH, CF₂═CFO(CF₂)₃COOH,

CF₂═CFOCF₂CF₂COOCH₃,

 CF₂═CFCF₂COOH, CF₂═CFCF₂CH₂OH,

and the like.

Examples of the fluorine-containing ethylenic monomer having functionalgroup and represented by the formula (4) are:

CF₂═CFCF₂OCF₂CF₂CF₂COOH,

and the like.

Examples of the fluorine-containing ethylenic monomer having functionalgroup and represented by the formula (5) are:

 CH₂═CFCF₂CF₂CH₂CH₂OH, CH₂═CFCF₂CF₂COOH,

and the like.

Examples of the fluorine-containing ethylenic monomer having functionalgroup and represented by the formula (6) are:

CH₂═CHCF₂CF₂CH₂CH₂COOH,

CH₂═CHCF₂₄CH₂CH₂CH₂OH,

CH₂═CHCF₂₆CH₂CH₂COOCH₃,

and the like.

In addition, there are:

and the like.

The fluorine-containing ethylenic monomer (b) having no functional groupwhich is copolymerized with the fluorine-containing ethylenic monomer(a) having functional group can be optionally selected from knownmonomers, and gives heat resistance, chemical resistance, non-stickingproperty, stain-proofing property and friction resistance to thepolymer.

Examples of the fluorine-containing ethylenic monomer (b) aretetrafluoroethylene, a monomer represented by the formula (2):CF₂═CF—R_(f) ¹, wherein R_(f) ¹ is CF₃ or OR_(f) ², in which R_(f) ² isa perfluoroalkyl group having 1 to 5 carbon atoms,chlorotrifluoroethylene, vinylidene fluoride, vinyl fluoride,hexafluoroisobutene,

CH₂═CFCF₂_(n)X², CH₂═CHCF₂_(n)X²,

wherein X² are selected from hydrogen atom, chlorine atom and fluorineatom, n are an integer of 1 to 5, and the like.

In addition to the fluorine-containing ethylenic monomer (a) havingfunctional group and the fluorine-containing ethylenic monomer (b)having no functional group, an ethylenic monomer having no fluorine atommay be copolymerized in the range of not lowering heat resistance andnon-sticking property. In that case, it is preferable that the ethylenicmonomer having no fluorine atom is selected from ethylenic monomershaving not more than 5 carbon atoms in order not to lower heatresistance. Examples of such an ethylenic monomer are ethylene,propylene, 1-butene, 2-butene, and the like.

A content of the fluorine-containing ethylenic monomer (a) havingfunctional group in the fluorine-containing ethylenic polymer havingfunctional group which is used in the present invention is from 0.05 to30% by mole on the basis of the whole monomers in the polymer. Furtherthe content is optionally selected depending on kinds of the surface ofa substrate for cooking apparatuses, shape of the substrate, coatingmethod, film forming method and conditions and further depending onpurposes and applications. The content of the fluorine-containingethylenic monomer (a) having functional group is preferably from 0.05 to20% by mole, particularly preferably from 0.1 to 10% by mole.

When the content of the fluorine-containing ethylenic monomer havingfunctional group is less than 0.05% by mole, sufficient adhesion to thesubstrate surface is difficult to obtain, and separation easily occursdue to temperature change and penetration of chemicals. When more than30% by mole, heat resistance is lowered, there occur adhesion failure,coloring, foaming and pin hole at sintering at high temperature orduring use at high temperature, thus easily lowering property forexhibiting clear surface pattern or causing separation of a coatinglayer and elution due to decomposition.

Examples of the preferred fluorine-containing ethylenic polymer havingfunctional group used in the present invention are as follows.

(I) A polymer comprising 0.05 to 30% by mole of the fluorine-containingethylenic monomer (a-1) having functional group and 70 to 99.95% by moleof tetrafluoroethylene (reactive PTFE).

The polymer is the most excellent in heat resistance, chemicalresistance and non-sticking property, and further is superior from theviewpoint of sliding property (friction resistance, abrasionresistance).

(II) A polymer comprising 0.05 to 30% by mole of the fluorine-containingethylenic monomer (a-1) having functional group based on the totalamount of monomers, and further based on the total amount of monomersexcluding the monomer (a-1), 85 to 99.7% by mole of tetrafluoroethyleneand 0.3 to 15% by mole of a monomer represented by the formula (2):

CF₂═CF—R_(f) ¹  (2)

wherein R_(f) ¹ is CF₃ or OR_(f) ², in which R_(f) ² is a perfluoroalkylgroup having 1 to 5 carbon atoms. For example, there is atetrafluoroethylene-perfluoro(alkyl vinyl ether) copolymer havingfunctional group (reactive PFA) or atetrafluoroethylene-hexafluoropropylene polymer having functional group(reactive FEP).

The polymer has heat resistance, chemical resistance and non-stickingproperty nearly equivalent to those of the above-mentioned reactive PTFE(I), and further is superior from the points of possessing transparencyand being melt-processable and from the viewpoint that even when coatedin the form of coating, it is possible to make the coating filmtransparent and its surface smooth by heat.

(III) A polymer comprising 0.05 to 30% by mole of thefluorine-containing ethylenic monomer (a-1) having functional groupbased on the total amount of monomers, and further based on the totalamount of monomers excluding the monomer (a-1), 40 to 80% by mole oftetrafluoroethylene, 20 to 60% by mole of ethylene and 0 to 15% by moleof other copolymerizable monomer (ethylene-tetrafluoroethylene polymer(III) having functional group (reactive ETFE)).

The polymer is superior from the viewpoint of excellent heat resistance,stain-proofing property, weather resistance and transparency, andfurther excellent mechanical strength, hardness and rigidity and fromthe point that molding and combining with other substrate (lamination,etc.) are easy because of good melt-flowability.

The fluorine-containing ethylenic polymer having functional group can beprepared by copolymerizing the fluorine-containing ethylenic monomer (a)having functional group and the fluorine-containing ethylenic monomer(b) having no functional group through known polymerization methods.Among them, radical copolymerization method is mainly used. Namely meansfor initiating the polymerization is not particularly limited if thepolymerization advances radically. For example, the polymerization isinitiated by an organic or inorganic radical polymerization initiator,heat, light, ionizing radiation, etc. The polymerization can be carriedout by solution polymerization, bulk polymerization, suspensionpolymerization, emulsion polymerization, or the like. A molecular weightof the polymer is regulated by a concentration of the monomers used inthe polymerization, a concentration of the initiator, and aconcentration of a chain transfer agent and polymerization temperature.Amounts of components of the prepared copolymer can be regulated byamounts of monomers used.

The fluorine-containing ethylenic polymer having functional group andexplained above can be made into various forms as a material to beapplied to a substrate. Represented examples of its application are acoating material or a material in the form of film. The polymer may beformed into a molded article.

In the present invention, the above-mentioned fluorine-containingethylenic polymer having functional group can be applied to a substratein the form of coating to give a composite material for cookingapparatuses.

In the present invention, in case of use in the form of coating, thepolymer is capable of being in the form of aqueous dispersion, organicsolvent dispersion, powder (including granulate), organosol or anaqueous emulsion of organosol. Among them, from environmental and safetypoints of view, it is preferable to apply in the form of an aqueousdispersion or powder (powder coating).

The coating may be applied so that excellent adhesive property of thefluorine-containing ethylenic polymer having functional group to thesubstrate is exhibited. The coating may be applied in one layer or as aprimer.

In the present invention, the aqueous dispersion for fluorine-containingcoating composition is prepared by dispersing, in water, particles ofthe above-mentioned fluorine-containing ethylenic polymer havingfunctional group. By introducing a functional group in thefluorine-containing polymer, dispersion stability of fine particles inthe aqueous dispersion is enhanced and a coating composition having goodstorage stability can be obtained, and further leveling property andtransparency of a coating film are enhanced.

As the fluorine-containing ethylenic polymer having functional group,from the viewpoint of heat resistance, non-sticking property, andfriction resistance, the reactive PTFE (I) is preferred, and from theviewpoint of heat resistance, non-sticking property and transparency,the reactive PFA or reactive FEP (II) is preferred.

The above-mentioned aqueous dispersion is preferably in a state of 0.01to 1.0 μm fine particles of the polymer being dispersed in water. Asurfactant may be blended in the aqueous dispersion for the purpose ofdispersion stability. Also to the aqueous dispersion can be addedadditives to be used usually such as pigment, surfactant, defoamingagent, viscosity control agent and leveling agent in amounts notlowering remarkably heat resistance, chemical resistance, non-stickingproperty and friction resistance.

The aqueous dispersion for fluorine-containing coating composition canbe prepared through various methods. Examples of the method are, forinstance,

a method wherein a powder of the fluorine-containing polymer havingfunctional group and prepared by suspension polymerization is finelypulverized and then the pulverized powder is dispersed homogeneouslyinto an aqueous dispersion medium with a surfactant,

a method wherein a fluorine-containing aqueous dispersion is prepared atthe same time as emulsion polymerization and further a surfactant andadditives are added as the case demands, and the like methods. From theviewpoint of productivity and quality (for making particle size smallerand more uniform), a method of preparing an aqueous dispersion directlyby emulsion polymerization is preferred.

A concentration of the polymer in the aqueous dispersion variesdepending on desired coating thickness, concentration and viscosity of acoating composition, coating method, etc., and is usually selected inthe range of from about 5% by weight to about 70% by weight.

The coating method is not particularly limited. The coating may becarried out by brush coating, spray coating, roll coating or the like,and then dried and sintered at a temperature of not less than themelting point of the polymer and not more than its decompositiontemperature depending on kind of the polymer.

The coating thickness may be selected depending on application, purpose,substrate, etc. For example, the coating thickness is from about 5 μm toabout 200 μm, preferably from 10 to 100 μm.

The powder coating composition of the present invention comprises apowder of the above-mentioned fluorine-containing ethylenic polymerhaving functional group.

Further from the viewpoint of heat resistance, non-sticking property,corrosion resistance and chemical resistance, the reactive PFA orreactive FEP (II) is preferred, and from the viewpoint of stain-proofingproperty, processability and transparency, the reactive ETFE (III) ispreferred.

As the fluorine-containing powder coating composition, there can be usedpreferably one in the form of powder or in the granular form having aparticle size of 10 to 1,000 μm and an apparent density of 0.3 to 1.2g/cc.

To the fluorine-containing powder coating composition can be addedoptionally additives in amounts not lowering remarkably characteristicssuch as heat resistance of the fluorine-containing resin. Examples ofthe additives are, for instance, pigments such as carbon powder,titanium oxide and cobalt oxide; reinforcing agents such as glass fiberpowder, carbon fiber powder and mica; amine anti-oxidant; organic sulfuranti-oxidant; organotin anti-oxidant; phenolic anti-oxidant; thermalstabilizer such as metal soap; leveling agent; anti-static agent; andthe like.

The fluorine-containing powder coating composition and the additives maybe admixed in the form of powder (dry method) or in the form of slurry(wet method), and the mixing in the form of powder is preferred. As themixing equipment, there can be used a conventional mixer or pulverizer,for example, a sand mill, V blender, ribbon blender or the like.

The fluorine-containing powder coating composition is generally coatedby electrostatic spray coating, fluidized-bed dip coating, rotolining,etc., and then sintered at a temperature of not less than the meltingpoint of the polymer and not more than its decomposition temperaturedepending on kind of the polymer, and thus a good coating film can beformed.

In general in case of electrostatic powder spray coating, a coating filmhaving a thickness of 10 to 200 μm is formed, and in case of rotolining,a coating film having a thickness of 200 to 1,000 μm is formed.

Further the fluorine-containing ethylenic polymer having functionalgroup which is used for a fluorine-containing coating material can beused, by utilizing its adhesive property, as a primer layer for afluorine-containing coating composition which has good heat resistanceat the time when applying a fluorine-containing resin having nofunctional group on surfaces of substrates such as metal and glass.

The primer for a fluorine-containing coating composition comprises theabove-mentioned fluorine-containing ethylenic polymer having functionalgroup.

As the primer, the same fluorine-containing polymer as mentioned abovecan be used. The primer is selected optionally depending on kind of asubstrate surface, kind of the fluorine-containing polymer to be appliedthrough the primer (kind of a top coat), etc. It is preferable ingeneral that the primer for a fluorine-containing coating composition isone which has the same structure as the fluorine-containing polymer tobe applied thereon and contains a functional group.

That combination of the primer and top coat assures good compatibilitybetween the fluorine-containing polymer to be used as the primer and thefluorine-containing polymer to be applied thereon, and can give not onlygood adhesion to the substrate surface but also good intercoat adhesivestrength between the primer layer and the top coat layer. Also even incase of the use at high temperature, unlike the case where the primermixed with other resin component is used, intercoat adhesion failure tobe caused due to a difference in thermal shrinkage between the polymers,cracking, pin hole, etc. are hard to arise. Further since the wholecoating film comprises the fluorine-containing polymer, it can be usedsufficiently for applications requiring transparency and vivid coloring.Still further excellent heat resistance, chemical resistance,non-sticking property and friction resistance can be exhibited moreeffectively even if a layer of fluorine-containing polymer having nofunctional group is formed on the outermost surface of the coating film.

Examples of the fluorine-containing polymer having no functional groupand used for a top coat layer are PTFE, PFA, FEP, ETFE, PVdF and VdFcopolymers.

As the primer for fluorine-containing coating composition, there can beused the above-mentioned fluorine-containing ethylenic polymer havingfunctional group. In case where a substrate is coated with PTFE, it ispreferable to use the primer selected from the reactive PTFE (I),reactive PFA and reactive FEP (II). It is particularly preferable touse, as the primer, thermo-melting reactive PFA or FEP (II) since it ispossible to thermo-melt and strongly adhere to a substrate surface bysintering. In case where a substrate is coated with PFA or FEP, it ispreferable to use, as the primer, reactive PFA or FEP (II). Further incase where a substrate is coated with ETFE, it is particularlypreferable to use, as the primer, reactive ETFE (III) from the viewpointof adhesion and transparency.

As a coating method using a primer layer, there can be used preferably amethod of coating a fluorine-containing polymer, which mainly comprisesthe following three steps;

(First step) a step for applying, to a substrate surface, the primer forfluorine-containing coating composition comprising the above-mentionedfluorine-containing polymer having functional group,

(Second step) a step for applying a fluorine-containing coatingcomposition comprising a fluorine-containing polymer having nofunctional group, to the primer layer formed in the above first step,and

(Third step) a step for sintering the laminated article obtained in theabove first and second steps.

Further the primer layer applied in the above first step may be set bydrying at 80° to 150° C. for about 5 minutes to about 30 minutes priorto the second step (2 coats/1 bake) or may be sintered, for example, ata temperature higher than the melting temperature thereof prior to thesecond step (2 coats/2 bakes).

The method for applying the primer in the first step is optionallyselected depending on the form of the primer. For example, in case wherethe fluorine-containing primer is in the form of aqueous dispersion,spray coating, spin coating, brush coating and dip coating methods areused. Also in case of the form of powder coating composition, coatingmethods such as electrostatic coating, fluid-bed dip coating androtolining are employed.

A thickness of the primer layer may vary depending on purpose,application, kind of a substrate surface and form of the primer. Thethickness is from 1 to 50 μm, preferably from 2 to 20 μm. Since thethickness of the primer is in general thin as mentioned above, it ispreferable to coat the primer in the form of aqueous dispersion by spraycoating, etc.

The method for applying the coating composition comprising afluorine-containing polymer having no functional group to the primerlayer in the second step is optionally selected depending on kind of thefluorine-containing polymer, form of the coating, purpose andapplication. For example, in case of an aqueous dispersion and organicsolvent dispersion, usually spray coating, brush coating, roll coatingand spin coating are carried out. In case of a powder coatingcomposition, electrostatic coating, fluid-bed dip coating or rotoliningare carried out.

A coating thickness of the fluorine-containing polymer in this stepvaries largely depending on purpose, application and coating method. Thethickness is in general from 5 to 50 μm, preferably from about 10 μm toabout 30 μm in case of spray coating. When a thick coating film isdesired by using a powder coating composition, it is possible to applyat 20 to 2,000 μm thick in case of electrostatic coating, and at 0.3 to10 μm thick in case of rotolining.

Sintering conditions in the third step are optionally selected dependingon kinds of fluorine-containing polymers (component, melting point,etc.) of the primer layer and the top layer thereon. The sintering iscarried out in general at a temperature of not less than the meltingpoint of the both fluorine-containing polymers. A sintering time variesdepending on the sintering temperature, and is from five minutes tothree hours, preferably from about 10 minutes to about 30 minutes. Forexample, when coating with PTFE, PFA and FEP, sintering is carried outat 320° to 400° C., preferably 350° to 400° C.

Then technique for applying the above-mentioned fluorine-containingethylenic polymer having functional group in the form of film to producea composite material for cooking apparatuses is explained.

Merits of applying in the form of film are as follows.

{circle around (1)} A film comprising a fluorine-containing ethylenicpolymer having functional group is advantageous from the viewpoint ofprocessing since an applicator necessary for a hot-melt adhesive is notrequired, and the film can be adhered by thermocompression bonding whilebeing put on a substrate or inserted between substrates.

{circle around (2)} Further since a uniform adhesive layer is formed onthe whole surface of substrate, a film free from nonuniform adhesion andhaving uniform adhesive strength can be obtained, and thus can beapplied to a substrate having poor or no compatibility therewith.

{circle around (3)} Further the film can be cut into various shapes, andthus is advantageous from the viewpoint of a small loss in processingwork, good working environment and cost.

The preferred fluorine-containing polymer film of the present inventionmay be one which is produced by molding the above-mentionedfluorine-containing ethylenic polymer having functional group. The filmcan be adhered to various substrates without surface treating and usingusual adhesives, thereby giving excellent characteristics of thefluorine-containing polymer to a substrate.

Though it is possible to produce adhesive films from the above-mentionedfluorine-containing polymers having functional group by using variousadhesives depending on application, purpose, film production process andadhering method, the above-mentioned copolymer (III) (reactive PFA orreactive FEP) or copolymer (IV) (reactive ETFE) is preferred since theadhesive film itself has heat resistance, chemical resistance,mechanical properties and non-sticking property; efficient film moldingrepresented by melt-molding can be carried out; the film has goodmoldability; making the film thin and uniform is possible; and it ispossible to melt the film by various thermocompression bonding methodsto adhere strongly and beautifully to various substrates. Particularlypreferred functional group is hydroxyl from the viewpoint of heatresistance.

A thickness of the fluorine-containing film is selected depending onpurpose and application and is not limited particularly. The thicknessis from 10 to 3,000 μm, preferably from 20 to 500 μm, particularlypreferably from 40 to 300 μm.

In case of too thin films, special production method is required; it isdifficult to handle the film at the time of adhering; wrinkling,breaking and poor appearance occur easily; and there is a case whereadhesive strength, mechanical strength, chemical resistance and weatherresistance become insufficient. Too thick film is disadvantageous fromthe viewpoint of cost and workability at the time of bonding to oneunit.

In the present invention, the fluorine-containing polymer film may beused alone or can be used in the form of laminated film comprising thefilm (adhesive layer) of fluorine-containing ethylenic polymer havingfunctional group and the film (surface layer) of fluorine-containingethylenic polymer having no functional group.

Namely one surface of the film is a layer comprising afluorine-containing ethylenic polymer having functional group and hasadhesive property to other substrate, and another surface of the film isa layer comprising usual fluorine-containing polymer. By bringing thesurface of the fluorine-containing ethylenic polymer having functionalgroup into contact to the substrate and adhering it to the substrate bythermocompression bonding, etc., excellent characteristics of thefluorine-containing polymer such as non-sticking property,stain-proofing property, friction resistance, weather resistance andchemical resistance can be given to the substrate for cookingapparatuses or the composite material comprising the substrate.

In the present invention, a thickness of the two-layered laminated filmof fluorine-containing polymer is selected depending on purpose andapplication, and is not limited particularly. The total thickness of twolayers is from 20 to 5,000 μm, preferably from 40 to 1,000 μm,particularly preferably from 100 to 500 μm.

A thickness of each layer which can be used is from 5 to 1,000 μm,preferably from 10 to 500 μm, particularly preferably from 10 to 200 μmof the adhesive layer, and from about 15 μm to about 4,995 μm,preferably from 30 to 990 μm, particularly preferably from 90 to 490 μmof the fluorine-containing polymer layer (surface layer).

The film for the surface layer may be adhered after adhering the filmfor the adhesive layer to a substrate.

To the film of fluorine-containing polymer having functional group canbe optionally incorporated proper additives such as a reinforcing agent,filler, stabilizer, ultraviolet ray absorber, pigment, etc. in an amountnot lowering characteristics of the film. Those additives make itpossible to improve thermal stability, surface hardness, abrasionresistance, weather resistance and electrostatic charge, etc.

The fluorine-containing film of the present invention can be produced,depending on kind of polymers used and desired shape of the film, byvarious methods such as thermal melting method, extrusion method,cutting method, solvent-casting method and a method of applying a powderor an aqueous dispersion or organic solvent dispersion to form acontinuous coating film.

For example, a polymer which comprises the above-mentioned reactive PTFEand is difficult to be melt-molded can be molded by compression molding,extrusion molding (ram extrusion, paste extrusion, roll press, etc.) orthe like. A polymer such as reactive PFA, FEP or ETFE which ismelt-moldable is molded by compression molding and extrusion molding,and melt-extrusion molding is particularly preferred from the viewpointof productivity and product quality.

Namely one surface of the film is a layer comprising afluorine-containing ethylenic polymer having functional group and hasadhesive property to other substrate, and another surface of the film isa layer comprising usual fluorine-containing polymer. By bringing thesurface of the fluorine-containing ethylenic polymer having functionalgroup into contact to the substrate and adhering it to the substrate bythermocompression bonding, etc., excellent characteristics of thefluorine-containing polymer such as chemical resistance, weatherresistance, stain-proofing property, non-sticking property, frictionresistance and electrical properties (high-frequency electric insulationproperty) can be given to the substrate or the composite materialcomprising the substrate.

In the present invention, a thickness of the two-layered laminated filmof fluorine-containing polymer is selected depending on purpose andapplication, and is not limited particularly. The total thickness of twolayers is from 20 to 5,000 μm, preferably from 40 to 1,000 μm,particularly preferably from 100 to 500 μm.

A thickness of each layer which can be used are from 5 to 1,000 μm,preferably from 10 to 500 μm, particularly preferably from 10 to 200 μmof the adhesive layer, and from about 15 μm to about 4,995 μm,preferably from 30 to 990 μm, particularly preferably from 90 to 490 μmof the fluorine-containing polymer layer (surface layer).

The film for the surface layer may be adhered after adhering the filmfor the adhesive layer to a substrate.

To the film of fluorine-containing polymer having functional group canbe optionally incorporated proper additives such as a reinforcing agent,filler, stabilizer, ultraviolet ray absorber, pigment, etc. in an amountnot lowering characteristics of the film. Those additives make itpossible to improve thermal stability, surface hardness, abrasionresistance, weather resistance and electrostatic charge, etc.

The fluorine-containing film of the present invention can be produced,depending on kind of polymers used and desired shape of the film, byvarious methods such as thermal melting method, extrusion method,cutting method, solvent-casting method and a method of applying a powderor an aqueous dispersion or organic solvent dispersion to form acontinuous coating film.

For example, a polymer which comprises the above-mentioned reactive PTFEand is difficult to be melt-molded can be molded by compression molding,extrusion molding (ram extrusion, paste extrusion, roll press, etc.) orthe like. A polymer such as reactive PFA, FEP or ETFE which ismelt-moldable is molded by compression molding and extrusion molding,and melt-extrusion molding is particularly preferred from the viewpointof productivity and product quality.

Bonding of the two films into one laminated film can be carried out by amethod of overlapping the respective molded films for adhesive layer andsurface layer and then compression-molding; a method of applying, to amolded film, the other one; a method of carrying out film molding andbonding of films at the same time through multi-layer co-extrusionmolding method, or the like method. Among them, the multi-layerco-extrusion molding method is preferred from the viewpoint ofproductivity and product quality.

Adhesion of the film of fluorine-containing polymer having functionalgroup to a substrate is achieved through thermal activation by heating,etc. Further thermo-melting adhesion is preferable. Represented examplesof the adhering method are heating roller method and heat press method.Also there are other methods such as high-frequency heating, microwaveheating, vacuum compression (vacuum press, etc.) and pneumatic press.Those methods can be optionally selected depending on kind and shape ofa substrate, condition and kind of film, etc.

Examples of the substrate on which the fluorine-containing polymerhaving functional group can be adhered, are a metallic substrate,ceramic substrate, resin substrate, and the like.

Metals of the metallic substrate encompass metal, alloys of two or moremetals, metal oxide, metal hydroxide, metal salts such as carbonate andsulfate, etc. Among them, metal, metal oxide and alloys are morepreferable from the viewpoint of adhesive property.

Examples of the metallic substrate are metals and metal compounds ofaluminum, iron, nickel, titanium, molybdenum, magnesium, manganese,copper, silver, lead, tin, chromium, beryllium, tungsten and cobalt,alloys of two or more thereof, etc.

Examples of the alloys are alloy steels such as carbon steel, Ni steel,Cr steel, Ni—Cr steel, Cr—Mo steel, stainless steel, silicon steel andPermalloy; aluminum alloys such as Al—Cl, Al—Mg, Al—Si, Al—Cu—Ni—Mg andAl—Si—Cu—Ni—Mg; copper alloys such as brass, bronze, silicon bronze,silicon brass, nickel silver and nickel bronze; nickel alloys such asnickel manganese (D nickel), nickel-aluminum (Z nickel), nickel-silicon,Monel metal, Constantan, nichrome Inconel and Hastelloy; and the like.

Further as the aluminum-based metal, there can be used pure aluminum;aluminum oxide; and aluminum alloys for casting and expanding such asAl—Cu, Al—Si, Al—Mg, Al—Cu—Ni—Mg, Al—Si—Cu—Ni—Mg alloys, high tensilealuminum alloy and corrosion resistant aluminum alloy.

Also as the iron-based metals, there can be used pure iron, iron oxide,carbon steel, Ni steel, Cr steel, Ni—Cr steel, Cr—Mo steel, Ni—Cr—Mosteel, stainless steel, silicon steel, Permalloy, non-magnetic steel,magnet steel, cast iron, etc.

Also the fluorine-containing polymer having functional group can beadhered to a substrate which was subjected to, for the purpose ofpreventing corrosion of metal, coating of other metal by electroplating,hot dipping, chromatizing, siliconizing, colorizing, sheradizing, metalspraying, etc.; forming a phosphate film by phosphatization; formingmetal oxide by anodizing or heat-oxidizing; or electrochemical corrosionprevention.

Further for the purpose of enhancing adhesion, the surface of metallicsubstrate may be subjected to chemical preparation with a phosphoricacid, sulfuric acid, chromic acid, oxalic acid, etc., or may besubjected to surface roughening by sand blasting, shot blasting, gritblasting, honing, paper scratching, wire scratching, hair linefinishing, etc. For the purpose of exhibiting clear surface pattern ofthe substrate, the metal surface may be subjected to coloring, printing,etching, etc.

In case of the above-mentioned aluminum or aluminum alloy substrate, inorder to enhance corrosion resistance, surface hardness and adhesiveproperty of the substrate, it is possible to form an oxide film(alumite) on the substrate by anodizing with caustic soda, oxalic acid,sulfuric acid or chromic acid and also use the aluminum or aluminumalloy substrate subjected to other surface treatments mentioned above.

Further there may be used a substrate plated, on its surface, othermetal as mentioned above, for example, steel plate subjected to hot-dipzinc-plating, hot-dip zinc alloy plating, aluminum plating, zinc-nickelplating, zinc-aluminum plating, or the like; a substrate coated withother metal by diffusion coating or thermal spraying; a substrate, onwhich an oxide film is formed by chemical conversion treatment withchromic acid or phosphoric acid or heat-treatment; a substrate subjectedto electric corrosion preventing treatment (for example, galvanizedsteel plate); or the like.

Examples of the ceramic substrate are, for instance, glass, pottery,porcelain, etc.

Components of glass are not particularly limited. Examples are silicaglass, lead glass, non-alkali glass, alkali glass, etc.

Examples of the resin substrate are, for instance, an acrylic resin,polycarbonate, heat resistant engineering plastic, thermosetting resin,etc.

Examples of the above-mentioned substrate used usually for the compositematerial for cooking apparatuses of the present invention as a metallicsubstrate are, for instance,

{circle around (1)} cold rolled steel sheet,

{circle around (2)} plated steel sheet, for example, Zn-plated steelsheet, Zn alloy-plated steel sheet, Al-plated steel sheet, Alalloy-plated steel sheet, Cr-plated steel sheet (TFS), Ni-plated steelsheet, Cu-plated steel sheet, galvanized steel sheet, etc.,

{circle around (3)} aluminum sheet,

{circle around (4)} titanium sheet,

{circle around (5)} stainless steel sheet, and the like.

In addition, where transparency is required, a ceramic substrate ofglass and a resin substrate of acrylic resin and polycarbonate areusually used.

It is preferable that the form of the substrate is the same as a form ofa finished product from the viewpoint that there is a case whereprocessability is difficult depending on kind of cooking apparatuses.

The composite material of the present invention can be used on variouscooking apparatuses firstly because the fluorine-containing resin isapplied to a substrate with good adhesive property and secondary becausethe fluorine-containing resin possesses good transparency (clear surfacepattern), heat resistance, non-sticking property, stain-proofingproperty, water- and oil repelling property, and the like.

Cooking apparatuses and parts thereof to which the composite materialfor cooking apparatuses of the present invention can be suitably appliedare classified by fields they belong to, and exemplified below.Accordingly the present invention also relates to cooking apparatusesand parts thereof mentioned below.

Also those classified cooking apparatuses and parts thereof are shown inTables 1 to 7.

{circle around (1)} Pots and Pans

(a) Inner surface, inner lid, etc. of electric pot including electricwater heater

In those applications, stain-proofing property (for fur), hot waterresistance and antibacterial property of the composite material forcooking apparatuses of the present invention can be used particularlyeffectively.

(b) Inner surface of inner pot, inner lid, etc. of gas and electric ricecookers and rice cookers with rice washing mechanism, etc.

In those applications, non-sticking property (for rice and scorching)and heat resistance of the composite material for cooking apparatuses ofthe present invention can be used particularly effectively.

{circle around (2)} Cooking Apparatuses

(a) Surfaces of frying pan, vat, household hand mixer for cooking,crate, kitchen knife, molder for bread, reverse sheet for rolling dough,dough dividing and rounding machine for bread, etc., inner surface ofmixing bowl, rice chest, etc. and blade of the above-mentioned mixer.

In those applications, non-sticking property (scorching and coheringstains), stain-proofing property and heat resistance of the compositematerial for cooking apparatuses of the present invention can be usedparticularly effectively.

(b) Inner surface, blade, etc. of electric food processors such aselectric food crusher for domestic use, electric food crusher, electricmeat grinder for kitchen use, electric blender for kitchen use andelectric mixer for kitchen use.

In those applications, non-sticking property (for vegetable and meatjuice) and stain-proofing property of the composite material for cookingapparatuses of the present invention can be used particularlyeffectively.

{circle around (3)} Gas Range with Grill

(a) Top panel, side panel, surface of gas ranges such as gas containerbuilt-in Type Range, and drip pan cover thereof, etc.

In those applications, non-sticking property (for oil stains), heatresistance and transparency (property for exhibiting clear color andpattern) of the composite material for cooking apparatuses of thepresent invention can be used particularly effectively.

{circle around (4)} Ranges with Oven Including Toaster, Range, etc.

(a) Inner surfaces (metallic portion) of ovens (range for kitchen) suchas oven for shop use, electric oven (including oven for shop use),electric oven with heating cabinet for shop use, cooking oven for shopuse and cooking range for shop use; ovens for making bread such asbaking oven for shop use and automatic baking apparatus for domesticuse; electric oven and toaster such as toaster and toaster for bread;and microwave range such as microwave range for shop use and microwaverange with oven; and pans for ranges.

In those applications, non-sticking property (for oil and scorching),stain-proofing property and heat resistance of the composite materialfor cooking apparatuses of the present invention can be usedparticularly effectively.

(b) Inner surface of door of ranges with oven raised in above (a)

In those applications, non-sticking property, heat resistance andtransparency of the composite material for cooking apparatuses of thepresent invention can be used particularly effectively. In case ofmicrowave range, energy ray resistance can be used particularlyeffectively.

{circle around (5)} Pots and Pans

(a) Inner surface of pots and pans such as glass pot, enameled pot,aluminum pot, electric frying pot, electric tempura pot, electricpressure pot and electric pressure pot for stew, etc.

In those applications, non-sticking property (for scorching, coheringstains and oil in case of the frying pot and Tempura pot) and heatresistance of the composite material for cooking apparatuses of thepresent invention can be used particularly effectively.

(b) Lid, etc. of pots and pans raised in above (a).

In those applications, not only the characteristics raised in above (a)but also transparency of the composite material for cooking apparatusesof the present invention can be used particularly effectively.

{circle around (6)} Garbage Disposer

Inner surface, etc. of garbage disposer for domestic use and garbage(waste) disposer for making compost.

In those applications, non-sticking property and stain-proofing propertyof the composite material for cooking apparatuses of the presentinvention can be used particularly effectively.

{circle around (7)} Other Heating Apparatuses for Cooking

(a) Heating surface, lid, etc. of griddle

In those applications, non-sticking property (for scorching and coheringstains) and heat resistance of the composite material for cookingapparatuses of the present invention and transparency thereof in case ofthe lid can be used particularly effectively.

(b) Cooking surface, etc. of electromagnetic cooking apparatuses such aselectromagnetic range and oven.

In those applications, non-sticking property, heat resistance andtransparency of the composite material for cooking apparatuses of thepresent invention can be used particularly effectively.

(c) Inner surface, door inner surface, lid, etc. of electric steamersuch as food steamer for shop use.

In those applications, non-sticking property, stain-proofing property,heat resistance and steam resistance of the composite material forcooking apparatuses of the present invention can be used particularlyeffectively.

(d) Inner surface, lid, etc. of noodle boiler for shop use.

In those applications, non-sticking property, stain-proofing property,heat resistance and hot water resistance of the composite material forcooking apparatuses of the present invention can be used particularlyeffectively.

(e) Inner surface, inner surface (metallic portion) and door innersurface of cooking roaster for shop use, pan for range, etc.

In those applications, non-sticking property (for scorching and coheringstains) and heat resistance of the composite material for cookingapparatuses of the present invention can be used particularlyeffectively.

(f) Inner surface, etc. of tableware and can washer for shop use

In those applications, non-sticking property, stain-proofing propertyand hot water resistance of the composite material for cookingapparatuses of the present invention can be used particularlyeffectively.

(g) Inner surface, door inner surface, etc. of heating cabinet for shopuse.

In those applications, non-sticking property, stain-proofing property,transparency and heat resistance of the composite material for cookingapparatuses of the present invention can be used particularlyeffectively.

Further examples of the cooking apparatuses other than those mentionedabove, to which the composite material for cooking apparatuses of thepresent invention can be preferably applied, are as follows.

Examples of cooking apparatuses within the range of above {circle around(1)} (b) are rice gruel cooker, rice warmer, etc.

Examples of cooking apparatuses within the range of above {circle around(2)} (a) are various cooking utensils (for slicing), cooking utensils,cooking appliance, cooking machine (for food, etc.), iron plate forcooking, cooking appliances and facilities, barbecue utensils, foodprocessing machine (with press machine, etc.), chocolate manufacturingmachine and ancillary temperature adjusting equipment thereof forstarting material, etc.

Examples of cooking appliances within the range of above {circle around(2)} (b) are cooking appliance for mixing, vegetable slicer, foodslicer, peeler, machine for cutting into cubes, food cutter, meatchopper, meat slicer, meat tenderizer, cutter mixer, mixer, food mixer,blender, apple processor, continuous egg opener, soy bean curd cutter,bread crumb coating machine, vegetable washer, etc.

Examples of cooking apparatuses within the range of above {circle around(3)} are range, portable heater, electric range, gas range, gas ovenwith grill, electric oven with grill, etc.

Examples of cooking apparatuses within the range of above {circle around(4)} are gas salamander, electric salamander, convention oven, bakingoven for making bread, etc.

Examples of cooking apparatuses within the range of above {circle around(5)} are wok set for Chinese dishes, one-handed pot, double-handed pot,gas fryer, Tempura fryer, oil filter unit, buckwheat pot, rotary pot,etc.

Examples of cooking apparatuses within the range of above {circle around(7)} are fryer for dumpling stuffed with minced meat, electromagneticrange, gas steamer, electric steamer, etc.

TABLE 1 Classifi- Typical cation finished Characteristics Defects ofEffect of the of product product needed prior art invention PotsElectric Stain-proofing Primer is Adhesive pot property for necessary.property, fur, hot water Process- processabil- resistance, ability isity (no antibacterial not good primer property and surface required)pattern is unclear. Electric Non-sticking Primer is Adhesive rice cookerproperty for necessary. property, scorched rice, Process- processabil-heat resistance ability is ity (no not good primer and surface required)pattern is unclear. Cooking Frying pan Non-sticking Process- Adhesiveappliances property for ability and property, and utensils scorch andtransparency processabil- cohered stain, are not good ity (nostain-proofing and surface primer property, heat pattern is required),resistance unclear. transparency, clearer surface pattern Electric foodNon-sticking Process- Adhesive processor property for ability andproperty, vegetable and transparency improvement juice of meat, are notgood of process- stain-proofing and surface ability (no property patternis primer unclear. required), transparency, clearer surface pattern Ovenwith Gas oven Non-sticking Process- Adhesive grill property for abilityis not property, stained oil, good and process- heat resistance surfaceability (no transparency, pattern is primer clear surface unclear.required), (color, pattern) transparency, clear surface pattern Rangewith Oven Non-sticking Process- Adhesive oven (kitchen property for oilability, heat property (toaster, range) and scorch, resistance(processabil- range) stain-proofing and durabil- ity), clear property,heat ity are not surface resistance, non- good. Wipe- pattern, stickingoff property transparency property, is not good transparency (Noarticles treated with fluorine-con- taining resin are avail- able).Trans- parency is not good. Oven for Non-sticking Process- Adhesivebaking bread property for oil ability, heat property and scorch,resistance (processabil- stain-proofing and durabil- ity), clearproperty, heat ity are not surface resistance, non- good. Wipe- pattern,sticking off property transparency property, is not good transparency(No articles treated with fluorine-con- taining resin are avail- able).Trans- parency is not good. Electric oven Non-sticking Process- Adhesiveand toaster property for oil ability, heat property and scorch,resistance (processabil- stain-proofing and durabil- ity), clearproperty, heat ity are not surface resistance, non- good. Wipe- pattern,sticking off property transparency property, is not good transparency(No articles treated with fluorine-con- taining resin are avail- able).Trans- parency is not good. Microwave Non-sticking Process- Adhesiveoven property, heat ability, heat property resistance, resistance(processabil- resistance to and durabil- ity), heat energy ray, ity arenot resistance, transparency good. Wipe- durability, off propertymaintenance is not good of transpar- (No articles ency treated withfluorine-con- taining resin are avail- able). Trans- parency is notgood.

TABLE 2 Classifi- Typical cation finished Characteristics Defects ofEffect of the of product product needed prior art invention Pot and panGlass pot Non-sticking Wipe-off Adhesive property for property isproperty scorch and not good (No (processabil- cohering stains, articlesity), trans- heat resistance, treated with parency transparencyfluorine- containing resin are available). Heat resist- ance andtransparency are not good. Electric deep Non-sticking Processabil-Adhesive fryer property for ity, heat property, oil, heat resistanceprocessabil- resistance, and wipe-off ity (no transparency property areprimer not good (No required), articles transparency treated withfluorine- containing resin are available). Surface pattern is unclear.Transpar- ency is not good. Electric pres- Non-sticking Processabil-Adhesive sure pot property ity, heat property, for scorching resistanceprocessabil- and cohering and wipe-off ity (no stains, heat property areprimer resistance, not good (No required), transparency articlestransparency treated with fluorine- containing resin are available).Surface pattern is unclear. Transpar- ency is not good. Electric pres-Non-sticking Processabil- Adhesive sure pot for property ity, heatproperty, stew for scorching resistance processabil- and cohering andwipe-off ity (no stains, heat property are primer resistance, not good(No required), transparency articles transparency treated with fluorine-containing resin are available). Surface pattern is unclear. Transpar-ency is not good.

TABLE 3 Classifi- Typical cation finished Characteristics Defects ofEffect of the of product product needed prior art invention OtherGriddle Non-sticking Processabil- Adhesive heating property for ity,abrasion property, appliances scorch and resistance processabil- forcooking cohering stains, and heat ity (no heat resistance, resistanceprimer non-sticking are not good. required), property, Wipe-off heatresist- transparency property is ance, abra- not good (No sion resist-articles ance, trans- treated with parency fluorine- containing resinare available). Transpar- ency is not good. Electro- Non-stickingProcessabil- Adhesive magnetic property, heat ity is not property,cooking resistance, good. processabil- appliance transparency ity (noprimer required), transparency Electric Non-sticking Processabil-Adhesive cooking property, stain- ity is not property, steamer proofinggood. processabil- property, ity (no heat resist- primer ance, steamrequired) resistance Noodles Non-sticking boiling property, stain-Processabil- Adhesive apparatus for proofing ity is not property, shopuse property, good. processabil- heat resist- ity (no ance, hot waterprimer resistance required) Other Cooking Non-sticking Processabil-Adhesive heating roaster for property for ity and heat property,applicances shop use scorch and resistance processabil- for cookingcohering stains, are not good. ity (no heat resistance primer required),transparency Tablewares Non-sticking Processabil- Adhesive and cansproperty, stain- ity is not property, washing proofing prop- good.processabil- machine for erty, hot water Surface ity (no shop useresistance pattern primer is unclear. required) Heat cabinetNon-sticking Processabil- Adhesive for shop use property, stain- ity andtrans- property, proofing prop- parency are processabil- erty, trans-not good. ity (no parency, Surface primer heat resistance pattern isrequired) unclear. Garbage Garbage Non-sticking Processabil- Adhesivedisposer disposer property, stain- ity is not property, proofing good.processabil- property Surface ity (no pattern primer is unclear.required)

TABLE 4 Classifi- Typical cation of finished product product Similarproduct Application Pots Electric pot Inner surface, inner lid Electricwater heater Inner surface, inner lid Electric rice Inner surface ofinner cooker pot, inner lid Rice cooker (gas, Inner surface of innerelectric) pot, inner lid Rice cooker (with Inner surface of inner ricewashing mech- pot, inner lid anism for shop use) Cooking Frying panSurface appliances Vat Surface and utensils Mixing bowl Inner surfaceChopping board Surface Household hand- Surface, blade operated mixer forcooking Crate Surface Cooking knife Surface Molder for making Surfacebread Reverse sheet for Surface making bread Dough dividing and Surfacerounding machine for making bread Rice chest Inner surface Electric foodInner surface, blade processor Household electric Inner surface foodcrusher Blade Electric food Inner surface crusher Blade Electric meatInner surface grinder for kitchen Blade use Electric blender for Innersurface kitchen use Blade Electric mixer for Inner surface kitchen useBlade Example of Preferred Applying Other substrate polymer* methodsimilar product Metal (aluminum, galvanized steel I, II Coating plate)Metal (aluminium, Rice gruel galvanized steel cooker, rice plate) I, IICoating warmer Metal Metal Metal Cooking utensils SUS, aluminum Cookingutensils SUS, aluminum (for slicing) Resin, wood Cooking utensils SUS,resin Cooking appli- SUS, resin I, II, III Coating ances and utensilsSUS Cooking appli- SUS ances (food) Metal Electric cooking Metalappliances Metal Cooking iron Cooking appli- ances and facil- itiesBarbecue utensils Food processing machine and utensils (with pressmachine) Metal Cooking appli- Metal ances for mixing, Metal vegetableslicer, Metal, glass food slicer, Metal peeler, cutter for Metal, glassI, II, III Coating cutting into small Metal cubes, food cut- Metal,glass ter, meat chopper, Metal meat slicer, meat Metal, glasstenderizer, cutter Metal mixer, mixer, food mixer, blender, appleprocessor, continuous egg opening machine, soy bean curd cutter, foodmolder, bread crumb coating machine, veget- able washing machine*Fluorine-containing ethylenic polymer (A) having functional group ofthe present invention

TABLE 5 Classifi- Typical cation of finished product product Similarproduct Application Gas oven Gas oven Top plate, side plate, with grillouter surface Gas container built- Top plate, side plate, in type gasoven outer surface Hood for drip pan Outer surface of gas oven (made ofmetal) Range with Oven Inner surface (metallic oven (toast- (kitchenportion), pan for er, range) range) range, Inner surface of door Ovenfor shop use Inner surface (metallic portion), pan for range, Innersurface of door Electric oven Inner surface (metallic portion), pan forrange, Inner surface of door Electric oven Inner surface (metallic (withheating portion), pan for cabinet for shop range, use) Inner surface ofdoor Electric oven (for Inner surface (metallic shop use) portion), panfor range, Inner surface of door Oven for shop use Inner surface(metallic portion), pan for range, Inner surface of door Cooking ovenfor Inner surface (metallic shop use portion), pan for range, Innersurface of door Cooking range for Inner surface (metallic shop useportion), pan for range, Inner surface of door Oven for Inner surface(metallic baking bread portion), pan for range, Inner surface of doorOven for baking Inner surface (metallic bread for shop use portion), panfor range, Inner surface of door Bread baker Inner surface (metallic(automatic, for portion), pan for domestic use) range, Inner surface ofdoor Example of Preferred Applying substrate polymer* method Othersimilar product Metal Portable range, oven with Metal I, II Coatinggrill, portable electric Metal range, gas range, gas oven with grillelectric oven with grill Metal Gas salamander, Metal, glass electricsalamaner, Metal convection oven Metal, glass Metal Metal, glass MetalMetal, glass Metal I, II Coating Metal, glass Metal Metal, glass MetalMetal, glass Metal Metal, glass Metal Oven for baking bread Metal, glassMetal Metal, glass I, II Coating Metal Metal, glass *Fluorine-containingethylenic polymer (A) having functional group of the present invention

TABLE 6 Classifi- Typical cation of finished product product Similarproduct Application Range with Electric oven Inner surface (metallicoven (toast- and toaster portion), pan for er, range) range, Innersurface of door Toaster Inner surface (metallic portion), pan for range,Inner surface of door Toaster for bread Inner surface (metallicportion), pan for range, Inner surface of door Microwave Inner surface(metallic oven portion), pan for range, Inner surface of door Microwaverange Inner surface (metallic for shop use portion), pan for range,range, Inner surface of door Microwave range Inner surface (metallicwith oven portion), pan for range, Inner surface of door Rice cookerInner surface (for microwave range) Pan and pot Glass pot Inner surface,lid Enamel pot Inner surface, lid Aluminum pot Inner surface, lidElectric Inner surface of pot, lid frying pot Inner surface of pot, lidElectric Tempura Inner surface of pot, lid frying pot Inner surface ofpot, lid Electric Inner surface of pot, lid pressure pot Inner surfaceof pot, lid Electric Inner surface of pot, lid pressure pot Innersurface of pot, lid for stew Example of Preferred Applying substratepolymer* method Other similar product Metal Metal, glass Metal Metal,glass I, II Coating Metal Metal, glass Metal Metal, glass Metal Metal,glass I, II Coating Metal Metal, glass Metal Glass Wok set for Chinesedishes, one-handed pot, double-handed pot Metal I, II Coating Gas fryer,electromagnet-    Glass ic fryer, Tempura fryer, Metal oil filter unit   Glass Metal Buckwheat boiling pot, I, II Coating rotary pot    GlassMetal I, II Coating    Glass *Fluorine-containing ethylenic polymer (A)having functional group of the present invention

TABLE 7 Classifi- Typical cation of finished product product Similarproduct Application Other Griddle Heating surface heating Lid applianceElectro- Cooking surface for cooking magnetic Electromagnetic Cookingsurface cooking range and oven appliance Electric Inner surface cookingInner surface of door steamer Food steamer for Inner surface shop useLid Noodle Inner surface boiling Lid apparatus for shop use CookingInner surface roaster for Inner surface of door shop use Cooking roasterfor Inner surface (metallic shop use portion), pan for range TablewaresInner surface and cans washing machine for shop use Heating Innersurface cabinet for Inner surface of door shop use Garbage Garbage Innersurface disposer disposer Garbage disposer Inner surface (wastes),garbage Inner surface disposer for house- Inner surface hould use,garbage disposer for making compost Example of Preferred Applyingsubstrate polymer* method Other similar product Metal Electric cookinggriddle Metal, glass I, II Coating for fried dumpling stuffed withminced pork Metal Electromagnetic range I, II Coating Metal Metal Gascooking steamer, Metal electric cooking steamer Metal I, II CoatingMetal, glass Metal I, II Coating Metal, glass Metal glass I, II CoatingMetal Metal } I, II, III } Coating Metal, glass } I, II, III } CoatingThawing box, food warmer, soup kettle, coffee maker, tea server, juicedispenser, miso soup dispenser, Sake warmer Metal Metal Metal I, II, IIICoating Metal, glass *Fluorine-containing ethylenic polymer (A) havingfunctional group of the present invention

EXAMPLE Preparation Example 1

Preparation of Aqueous Dispersion Comprising PFA having Hydroxyl

A 3-liter glass-lined autoclave equipped with a stirrer, valve, pressuregauge and thermometer was charged with 1,500 ml of pure water and 9.0 gof ammonium perfluorooctanoate. After replacing with nitrogen gassufficiently, the autoclave was evacuated and charged with 20 ml ofethane gas.

Then 3.8 g ofperfluoro-(1,1,9,9-tetrahydro-2,5-bistrifluoromethyl-3,6-dioxa-8-nonenol)(formula (7)):

and 18 g of perfluoro(propyl vinyl ether) (PPVE) were fed into theautoclave with pressurized nitrogen, and a temperature inside the systemwas maintained at 70° C.

Pressurized tetrafluoroethylene (TFE) gas was introduced into theautoclave with stirring so that the inside pressure of the autoclavebecame 8.5 kgf/cm²G.

Then a solution prepared by dissolving 0.15 g of ammonium persulfate in5.0 g of water was added with pressurized nitrogen gas to initiate thereaction.

Since the pressure lowered with the advance of the polymerizationreaction, it was increased again to 8.5 kgf/cm²G by feedingtetrafluoroethylene gas at the time when it lowered to 7.5 kgf/cm²G.Thus the decreasing and increasing of the pressure was repeated.

With continuing supply of tetrafluoroethylene, every time when about 40g of tetrafluoroethylene gas was consumed after starting of thepolymerization, 1.9 g of the above-mentioned fluorine-containingethylenic monomer having hydroxyl (compound represented by the formula(7)) was introduced under pressure three times (5.7 g in total) tocontinue the polymerization. At the time when about 160 g oftetrafluoroethylene gas was consumed after starting of thepolymerization, the supplying thereof was terminated and the autoclavewas cooled and the un-reacted monomer was released to give 1,702 g of abluish semi-transparent aqueous dispersion.

A concentration of the polymer in the obtained aqueous dispersion was10.9%, and a particle size measured by dynamic light scattering methodwas 70.7 nm.

Also a part of the obtained aqueous dispersion was sampled and subjectedto freeze coagulation, and the precipitated polymer was rinsed and driedto isolate a white solid. Components and their amounts of the obtainedcopolymer which were determined through ¹⁹F-NMR and IR analyses wereTFE/PPVE/(Fluorine-containing ethylenic monomer having hydroxyl andrepresented by the formula (7))=97.7/1.2/1.1% by mole.

In infrared spectrum, characteristic absorption of —OH was observed at3,620 to 3,400 cm⁻¹.

According to DSC analysis, Tm was 310° C., and according to DTGAanalysis, 1% thermal decomposition temperature Td was 368° C. A meltflow rate measured under conditions of preheating at 372° C. for fiveminutes at a load of 7 kgf/cm² by using Koka-type flow tester andnozzles of 2 mm×8 mm length was 12.0 g/10 min.

Preparation Example 2

Preparation of Aqueous Dispersion Comprising PFA having Hydroxyl

The same autoclave as in Preparation Example 1 was charged with 1,500 mlof pure water and 9.0 g of ammonium perfluorooctanoate. After replacingwith nitrogen gas sufficiently, the autoclave was evacuated and chargedwith 20 ml of ethane gas.

Then 1.9 g ofperfluoro-(1,1,9,9-tetrahydro-2,5-bistrifluoromethyl-3,6-dioxa-8-nonenol)(compound of the formula (7)) and 16.1 g of perfluoro(propyl vinylether) (PPVE) were fed into the autoclave with pressurized nitrogen gas,and a temperature inside the system was maintained at 70° C.

Pressurized tetrafluoroethylene (TFE) gas was introduced into theautoclave with stirring so that the inside pressure became 8.5 kgf/cm²G.

Then a solution prepared by dissolving 0.15 g of ammonium persulfate in5.0 g of water was fed with pressurized nitrogen gas to initiate thereaction.

Since the pressure lowered with the advance of the polymerizationreaction, at the time when the pressure lowered down to 7.5 kgf/cm²G, itwas increased again to 8.5 kgf/cm²G with tetrafluoroethylene gas, andthe decreasing and increasing of the pressure were repeated.

With continuing supply of tetrafluoroethylene, every time when 40 g oftetrafluoroethylene gas was consumed after starting of thepolymerization, 0.95 g of the fluorine-containing ethylenic monomerhaving hydroxyl (compound represented by the formula (7)) was introducedthree times (2.85 g in total) under pressure to continue thepolymerization. When 160 g of tetrafluoroethylene was consumed afterstarting of the polymerization, the supplying thereof was terminated.The autoclave was cooled and the un-reacted monomer was released to give1,692 g of an aqueous dispersion. A concentration of the polymer in theobtained aqueous dispersion was 10.6% and a particle size thereof was76.8 nm.

A part of the aqueous dispersion was sampled, and a white solid wasisolated in the same manner as in Preparation Example 1.

Analysis of the obtained white solid indicates:

TFE/PPVE/(Fluorine-containing monomer having hydroxyl and represented bythe formula (7))=98.3/1.1/0.6% by mole

Tm=310° C.

1% Thermal decomposition temperature Td=374° C.

Melt flow rate: 9.5 g/10 min

In infrared spectrum, characteristic absorption of —OH was observed at3,620 to 3,400 cm⁻¹.

Preparation Example 3

Synthesis of Aqueous Dispersion of PFA having No Functional Group

Emulsion polymerization was carried out in the same manner as inPreparation Example 1 except thatperfluoro-(1,1,9,9-tetrahydro-2,5-bistrifluoromethyl-3,6-dioxa-8-nonenol)(compound of the formula (7)) was not used, and 1,662 g of an aqueousdispersion of PFA having no functional group was obtained.

A concentration of the polymer in the aqueous dispersion was 9.7%, and aparticle size thereof was 115 nm.

A white solid was isolated and analyzed in the same manner as inPreparation Example 1.

TFE/PPVE=98.9/1.1% by mole

Tm=310° C.

1% Thermal decomposition temperature Td=479° C.

Melt flow rate: 19.2 g/10 min

In infrared spectrum, no characteristic absorption of —OH was observed.

Preparation Example 4

Synthesis of PFA having Hydroxyl

A 6-liter glass-lined autoclave equipped with a stirrer, valve, pressuregauge and thermometer was charged with 1,500 ml of pure water. Afterreplacing with nitrogen gas sufficiently, the autoclave was evacuatedand charged with 1,500 g of 1,2-dichloro-1,1,2,2-tetrafluoroethane(R-114).

Then 5.0 g ofperfluoro-(1,1,9,9-tetrahydro-2,5-bistrifluoromethyl-3,6-dioxa-8-nonenol)(compound of the formula (7)), 130 g of perfluoro(propyl vinyl ether)(PPVE) and 180 g of methanol were fed into the autoclave withpressurized nitrogen gas, and a temperature inside the system wasmaintained at 35° C.

Pressurized tetrafluoroethylene (TFE) gas was introduced into theautoclave with stirring so that the inside pressure became 8.0 kgf/cm²G. Then 0.5 g of a 50% methanol solution of di-n-propyl peroxydicarbonatewas fed with pressurized nitrogen to initiate the reaction.

Since the pressure lowered with the advance of the polymerizationreaction, at the time when the pressure lowered down to 7.5 kgf/cm²G, itwas increased again to 8.0 kgf/cm²G, and the decreasing and increasingof the pressure were repeated.

With continuing supply of tetrafluoroethylene, every time when about 60g of tetrafluoroethylene gas was consumed after starting of thepolymerization, 2.5 g of the fluorine-containing ethylenic monomerhaving hydroxyl (compound represented by the formula (7)) was introducednine times (22.5 g in total) under pressure to continue thepolymerization. When about 600 g of tetrafluoroethylene was consumedafter starting of the polymerization, the supplying thereof wasterminated. The autoclave was cooled and the un-reacted monomer andR-114 were released.

The obtained copolymer was washed with water, rinsed with methanol andthen vacuum-dried to give 710 g of a white solid. The composition of theobtained copolymer was TFE/PPVE/(Fluorine-containing ethylenic monomerhaving hydroxyl and represented by the formula (7))=97.0/2.0/1.0% bymole according to ¹⁹F-NMR and IR analyses. In infrared spectrum,characteristic absorption of —OH was observed at 3,620 to 3,400 cm⁻¹.According to DSC analysis, Tm was 305° C., and according to DTGAanalysis, 1% thermal decomposition temperature Td was 375° C. A meltflow rate measured under conditions of preheating at 372° C. for fiveminutes at a load of 7 kgf/cm² by using Koka-type flow tester andnozzles of 2 mm diameter×8 mm length was 32 g/10 min.

Preparation Example 5

Synthesis of PFA having Hydroxyl

A 6-liter glass-lined autoclave equipped with a stirrer, valve, pressuregauge and thermometer was charged with 1,500 ml of pure water. Afterreplacing with nitrogen gas sufficiently, the autoclave was evacuatedand charged with 1,500 g of 1,2-dichloro-1,1,2,2-tetrafluoroethane(R-114).

Then the reaction was initiated in the same manner as in PreparationExample 4 except that 2.5 g ofperfluoro-(1,1,9,9-tetrahydro-2,5-bistrifluoromethyl-3,6-dioxa-8-nonenol),132 g of perfluoro(propyl vinyl ether) (PPVE) and 230 g of methanol wereused. A temperature inside the system was maintained at 35° C.

Pressurized tetrafluoroethylene (TFE) gas was introduced into theautoclave with stirring so that the inside pressure of the autoclavebecame 8.0 kgf/cm²G. Then 0.5 g of a 50% methanol solution ofdi-n-propyl peroxydicarbonate was added with pressurized nitrogen gas toinitiate the reaction.

Since the pressure lowered with the advance of the polymerizationreaction, it was increased again to 8.0 kgf/cm²G by feedingtetrafluoroethylene gas at the time when it lowered to 7.5 kgf/cm²G.Thus the decreasing and increasing of the pressure was repeated.

Further 680 g of a white solid copolymer was obtained in the same manneras in Preparation Example 4 except that every time when about 60 g oftetrafluoroethylene gas was consumed after starting of thepolymerization, 1.23 g of the above-mentioned fluorine-containingethylenic monomer having hydroxyl (compound represented by the formula(7)) was introduced under pressure nine times (11.10 g in total).Components and their amounts of the obtained copolymer which weredetermined through ¹⁹F-NMR and IR analyses wereTFE/PPVE/(Fluorine-containing ethylenic monomer having hydroxyl andrepresented by the formula (7))=97.6/2.0/0.4% by mole. In infraredspectrum, characteristic absorption of —OH was observed at 3,620 to3,400 cm⁻¹. According to DSC analysis, Tm was 310° C., and according toDTGA analysis, a decomposition starting temperature was 368° C. and 1%thermal decomposition temperature Td was 375° C. A melt flow ratemeasured under conditions of preheating at 372° C. for five minutes at aload of 7 kgf/cm² by using Koka-type flow tester and nozzles of 2 mmdiameter×8 mm length was 42 g/10 min.

Preparation Example 6

Synthesis of PFA having No Functional Group

Synthesis was carried out in the same manner as in Preparation Example 4except thatperfluoro-(1,1,9,9-tetrahydro-2,5-bistrifluoromethyl-3,6-dioxa-8-nonenol)(compound of the formula (7)) was not used and 240 g of methanol wasused, and 597 g of PFA having no functional group was obtained.

The obtained PFA was analyzed in the same manner as in PreparationExample 4 and the results were as follows.

TFE/PPVE=98.2/1.8% by mole

Tm=310° C.

Td=469° C. (1% weight reduction)

Melt flow rate: 24 g/10 min

Preparation Example 7

Preparation of PFA Powder Coating Composition having Hydroxyl

The PFA powder having hydroxyl and prepared in Preparation Example 4(apparent specific gravity: 0.5, true specific gravity: 2.1, averageparticle size: 600 μm) was compressed into a sheet of 60 mm wide×5 mmthick by a Roller Compactor (Model BCS-25 available from Shinto KogyoKabushiki Kaisha), and then crushed into about 10 mm diameter by acrusher and further finely pulverized at room temperature at 11,000 rpmby a pulverizer (Cosmomizer Model N-1 available from Nara KikaiSeisakusho). Subsequently the coarse powder particles of not less than170 mesh (88 μm of sieve opening) were separated by a classifier(Hibolder Model 300SD available from Shi-Tokyo Kikai Kabushiki Kaisha)to give a PFA powder coating composition having hydroxyl. An apparentdensity of the powder was 0.7 g/ml, and an average particle size thereofwas 20 μm.

Preparation Example 8

Preparation of PFA Powder Coating Composition having No Functional Group

A PFA powder coating composition was prepared in the same manner as inPreparation Example 7 except that the PFA powder having no functionalgroup and prepared in Preparation Example 6 (apparent specific gravity:0.6, true specific gravity: 2.1, average particle size: 400 μm) was usedinstead of the PFA powder having hydroxyl and prepared in PreparationExample 4. An apparent density of the obtained powder was 0.73 g/ml, andan average particle size thereof was 20 μm.

Preparation Example 9

Synthesis of Fluorine-containing Polymer Prepared by Using aNon-fluorine-containing Monomer having Functional Group

A 1-liter stainless steel autoclave equipped with a stirrer, valve,pressure gauge and thermometer was charged with 250 g of butyl acetate,36.4 g of vinyl pivalate (VPi) and as a non-fluorine-containing monomerhaving hydroxyl, 32.5 g of 4-hydroxybutyl vinyl ether (HBVE) and 4.0 gof isopropoxycarbonyl peroxide. After cooling to 0° C. with ice andreplacing with nitrogen gas sufficiently, the autoclave was evacuatedand charged with 47.5 g of isobutylene (IB) and 142 g oftetrafluoroethylene (TFE).

The autoclave was heated to 40° C. and reaction was carried out for 30hours with stirring. At the time when the inside pressure of thereaction vessel is lowered to not more than 2.0 kg/cm², the reaction wasterminated. The autoclave was cooled and un-reacted gas monomer wasreleased, and thus a butyl acetate solution of a fluorine-containingpolymer was obtained. A polymer concentration was 45%.

A fluorine-containing polymer was separated from the obtained butylacetate solution of fluorine-containing polymer through re-precipitationmethod, followed by sufficiently reducing pressure and drying, thusbeing separated in the form of white solid. According to ¹H-NMR and¹⁹F-NMR elementary analyses, the obtained fluorine-containing polymerwas a copolymer of TFE/IB/VPi/HBVE=44/34/15/7% by mole.

Preparation Example 10

Production of Film of PFA having Hydroxyl

A metal die of 100 mm diameter was charged with 8.0 g of the white solidobtained in Preparation Example 4 and set on a press machine of 350° C.,followed by preheating for 30 minutes and then compression-molding at 70kg/cm² for one minute. Thus a 0.5 mm thick film was obtained.

Preparation Example 11

Production of Film of PFA having Hydroxyl

The same procedures as in Preparation Example 10 were repeated exceptthat the white solid obtained in Preparation Example 5 was used, to givea 0.5 mm thick film.

Preparation Example 12

Production of Film of PFA having No Functional Group

The same procedures as in Preparation Example 10 were repeated exceptthat the white solid obtained in Preparation Example 6 was used, to givea 0.5 mm thick film.

Preparation Example 13

Production of Film of PFA having Hydroxyl by Extrusion

The white solid obtained in Preparation Example 4 was extruded at 350°to 370° C. by using a biaxial extruder (LABOPLASTOMIL available fromToyo Seiki Kabushiki Kaisha) to give pellets. The pellets were extrudedat 360° to 380° C. at a roll temperature of 120° C. by using a uniaxialextruder (LABOPLASTOMIL available from Toyo Seiki Kabushiki Kaisha) togive a film of 10 cm wide×100 to 150 μm thick.

Preparation Example 14

Production of Film of PFA having No Functional Group by Extrusion

The same procedures as in Preparation Example 13 were repeated exceptthat the white solid obtained in Preparation Example 6 was used, to givepellets. Further extrusion was carried out in the same manner as inPreparation Example 17 to give a film of 10 cm wide×100 to 150 μm thick.

Preparation Example 15

Production of Laminated Film of PFA having Hydroxyl and PTFE

The film of PFA having hydroxyl and obtained in Preparation Example 13and a 0.5 mm thick PTFE film were overlapped and compression-molded inthe same manner as in Preparation Example 10.

The two layers were adhered strongly.

Example 1

(1) Pre-treatment of Substrate

A 1.5 mm thick pure aluminum plate (A1050P) and a 1.5 mm thick SUS304plate were degreased respectively with acetone.

(2) Formation of Primer Layer Comprising Fluorine-containing Polymerhaving Functional Group

An aqueous dispersion comprising PFA having hydroxyl and prepared inPreparation Example 1 was applied to the plate by an air spray so that acoating thickness would become about 5 μm, followed by infrared-dryingat 90° C. for 10 minutes and sintering at 380° C. for 20 minutes.

(3) Formation of Layer (Top Layer) Comprising Fluorine-containingPolymer having No Functional Group

Onto the primer layer obtained in (2) above was applied an aqueouscoating composition of PTFE (POLYFLON TFE Enamel EK4300CRN availablefrom DAIKIN INDUSTRIES, LTD.) as a coating composition offluorine-containing polymer having no functional group by an air sprayso that a coating thickness would become about 20 μm, followed byinfrared-drying at 90° C. for 10 minutes and sintering at 380° C. for 20minutes.

(4) Evaluation of Adhesive Property

The method of evaluation is as follows.

Cross-cut Adhesion Test

According to JIS K 5400 1990, 8. 5. 2, a coated surface was cross-cut togive 100 squares, and an adhesive tape (available from NichibanKabushiki Kaisha) is adhered to the cross-cut surface sufficiently. Thenimmediately the tape is torn off. This is repeated 10 times with newadhesive tapes to check to see how many squares remain among 100squares. The results are shown in Table 8.

Example 2

A coated plate was produced in the same manner as in Example 1 exceptthat a primer layer was formed by using the aqueous dispersioncomprising PFA having hydroxyl and obtained in Preparation Example 2 asa primer comprising a fluorine-containing polymer having functionalgroup. The evaluation for adhesive property was carried out, and theresults are shown in Table 8.

Comparative Example 1

A coated plate was produced in the same manner as in Example 1 exceptthat a primer layer was formed by using the aqueous dispersioncomprising PFA having no functional group and obtained in PreparationExample 3 instead of a primer comprising a fluorine-containing polymerhaving functional group. The evaluation for adhesive property wascarried out, and the results are shown in Table 8.

Examples 3 and 4 and Comparative Example 2

Coated plates were produced in the same manner as in Example 1 in caseof Example 3, in Example 2 in case of Example 4 and in ComparativeExample 1 in case of Comparative Example 2 except that a top layer wasformed by using an aqueous coating composition comprising FEP (NEOFLONFEP Dispersion ND-1 available from DAIKIN INDUSTRIES, LTD) as a coatingcomposition comprising a fluorine-containing polymer having nofunctional group. The evaluation for adhesive property was carried out,and the results are shown in Table 8.

Example 5

(1) Pre-treatment of Substrate

Pre-treatment was carried out in the same manner as in Example 1.

(2) Formation of Primer Layer Comprising Fluorine-containing Polymerhaving Functional Group

An aqueous dispersion comprising PFA having hydroxyl and prepared inPreparation Example 1 was applied to the plate by an air spray so that acoating thickness would become about 5 μm, followed by infrared-dryingat 90° C. for 10 minutes.

(3) Formation of Layer (Top Layer) Comprising Fluorine-containingPolymer having No Functional Group

Onto the primer layer obtained in (2) above was applied a powder coatingcomposition of PFA (NEOFLON PFA Powder Coating Composition ACX-31available from DAIKIN INDUSTRIES, LTD.) as a coating composition offluorine-containing polymer having no functional group by electrostaticcoating so that a coating thickness would become 40 μm, followed bysintering at 380° C. for 20 minutes.

(4) Evaluation of Adhesive Property

The evaluation was carried out in the same manner as in Example 1, andthe results are shown in Table 8.

Example 6

A coated plate was produced in the same manner as in Example 5 exceptthat a primer layer was formed by using the aqueous dispersioncomprising PFA having hydroxyl and obtained in Preparation Example 2 asa primer comprising a fluorine-containing polymer having functionalgroup. The evaluation for adhesive property was carried out, and theresults are shown in Table 8.

Comparative Example 3

A coated plate was produced in the same manner as in Example 5 exceptthat a primer layer was formed by using the aqueous dispersioncomprising PFA having no functional group and obtained in PreparationExample 3 instead of a primer comprising a fluorine-containing polymerhaving functional group. The evaluation for adhesive property wascarried out, and the results are shown in Table 8.

Example 7

Evaluation of Adhesive Property of PFA Powder Coating Composition havingHydroxyl

(1) Production of Press Sheet for Adhesion Test

About 4 kg of the powder coating composition having hydroxyl andprepared in Preparation Example 7 was put in a cylindrical metal mold of60 mm diameter and compression-molded at room temperature at a pressureof 300 kgf/cm² with a press machine to give a disc-like cold press sheet(hereinafter also referred to as “PFA sheet”).

(2) Pre-treatment of Substrate

A pure aluminum plate of 100×100×1 (mm) was degreased with acetone andthen subjected to sand blasting.

(3) Production of Adhered Sample

The PFA sheet obtained in (1) above was placed on the aluminum plate((2) above) and put in a hot air dryer to heat and melt at 330° C. for10 minutes. Thus a sample produced by adhering the PFA sheet of about450 μm thick to the aluminum plate was obtained. FIG. 1 shows adiagrammatic plan view of the adhered plate comprising the PFA sheet 1and the aluminum plate 2.

(4) Measurement of Adhesive Strength

As shown in FIG. 1, the PFA sheet 1 of the adhered sample obtained in(3) above was cut with a cutter at intervals of a width a (10 mm) andone end of strip-like sheet 1 was folded up, thus giving a test samplefor measuring adhesive strength. FIG. 2 shows a diagrammatic perspectiveview of the test sample for measuring adhesive strength. As shown inFIG. 2, the sheet 1 was pulled up at an angle of 90° to the aluminumplate 2 to measure adhesive strength. The adhesive strength was measuredat room temperature at a cross head speed of 50 mm/min with TENSILONUniversal Tester (available from Orientec Corporation). An adhesivestrength was 5.5 kgf/cm as an average value of peel by area method.

Comparative Example 4

Evaluation of Adhesive Property of PFA Powder Coating Composition havingNo Functional Group

Production of a press sheet for adhesion test, pre-treatment of asubstrate and production of an adhered sample were carried out in thesame manner as in Example 7 except that the powder coating compositionof PFA having no functional group and prepared in Preparation Example 8was used instead of the powder coating composition of PFA havinghydroxyl and prepared in Preparation Example 7. Then adhesive strengthwas measured.

Adhesive strength of the powder coating composition of PFA having nofunctional group was 0.8 kgf/cm.

Example 8

Electrostatic Coating of PFA Powder Coating Composition having Hydroxyl

Electrostatic coating of the PFA powder coating composition havinghydroxyl and prepared in Preparation Example 7 was carried out on analuminum plate pre-treated in the same manner as in Example 7 at roomtemperature at a voltage of 40 kV with an electrostatic coating machine(Model GX3300 available from Iwata Toso Kabushiki Kaisha). The coatedplate was sintered at 330° C. for 15 minutes with a hot air dryer togive a coating film.

The coating film was a continuous uniform transparent film and wasadhered strongly to the aluminum plate.

Comparative Example 5

Heat Resistance of Fluorine-containing Polymer Prepared by UsingNon-fluorine-containing Monomer having Functional Group

Thermal decomposition temperature of the fluorine-containing polymerprepared in Preparation Example 9 was measured through TGA analysis, and1% thermal decomposition temperature was 220° C. Thereby it is seen thatheat resistance of the fluorine-containing polymer prepared by using anon-fluorine-containing monomer having functional group like the polymerobtained in Preparation Example 9 is low.

Further the fluorine-containing copolymer obtained in PreparationExample 9 was dissolved in butyl acetate in a concentration of 10% byweight.

Pre-treatment of a pure aluminum substrate, application of a primerlayer comprising the fluorine-containing copolymer of PreparationExample 9 and application (electrostatic coating of PFA powder coatingcomposition) of a top layer were carried out in the same manner as inExample 5 except that for the primer layer, a butyl acetate solution ofthe fluorine-containing copolymer of Preparation Example 9 was usedinstead of the aqueous dispersion of PFA having hydroxyl.

A coating film obtained by sintering at 380° C. for 20 minutes after theapplication was colored yellow-brown, and foaming and peeling were alsoseen. Thus a uniform transparent coating film could not be obtained.

TABLE 8 Com. Com. Com. Ex. 1 Ex. 2 Ex. 1 Ex. 3 Ex. 4 Ex. 2 Ex. 5 Ex. 6Ex. 3 Fluorine-containing Prep. Prep. Prep. Prep. Prep. Prep. Prep.Prep. Prep. aqueous dispersion Ex. 1 Ex. 2 Ex. 3 Ex. 1 Ex. 2 Ex. 3 Ex. 1Ex. 2 Ex. 3 used for primer layer Fluorine-containing PTFE PTFE PTFE FEPFEP FEP PFA PFA PFA resin forming top layer Evaluation of adhesion(Cross-out adhesion test) SUS304 100/100 100/100 0/100 100/100 100/100 0/100 100/100 100/100 20/100 Pure aluminum 100/100 100/100 0/100100/100 100/100 20/100 100/100 100/100 30/100

Examples 9 to 12

Adhesion Test of PFA Film having Hydroxyl to Metal

Adhesion test of a PFA film having hydroxyl (Film of Preparation Example10 or 11) to a metal plate was carried out in the manner mentioned belowby using degreased chromate-treated aluminum, pure aluminum and steelplates of 0.5 mm thick. The results are shown in Table 9.

Production of Test Piece for Peeling Test

FIG. 3 is a diagrammatic perspective view of a laminated article made toproduce a test piece for peeling test. As shown in FIG. 3, the PFA filmhaving hydroxyl and obtained in Preparation Examples 10 or 11 as anadhesive layer 3 and a 0.1 mm thick spacer 4 (aluminum foil) were putbetween the two metal plates 5 and then set on a press machine of 350°C., followed by preheating (20 minutes) and then compressing at 50kg/cm² for one minute to give a laminated article of length b (150mm)×width c (70 mm).

A thickness of the respective adhesive layers 3 of the obtainedlaminated articles was 0.1 mm. Further the laminated article was cut toa width d of 25 mm and the spacer portion is bent in the shape of T at apoint apart by a distance e (100 mm) from one end of the laminatedarticle to give a test piece for the peeling test. FIG. 4 is adiagrammatic perspective view of the obtained test piece for peelingtest. In FIG. 4, numeral 3 represents an adhesive layer and numeralrepresents metal plates.

Peeling Test

The peeling test was carried out at room temperature at a cross headspeed of 50 mm/min by using TENSILON Universal Tester available fromOrientec Corporation according to T-type peeling test method of JISK6854-1977. The results show the maximum peeling strength (kgf/25 mm)and minimum peeling strength (kgf/25 mm)

Comparative Examples 6 to 8

Adhesion Test of PFA Film having No Functional Group to Metal

Production of test pieces and peeling test were carried out in the samemanner as in Example 9 except that the PFA films having no functionalgroup and obtained in Preparation Example 12 were used instead of thePFA films having hydroxyl and obtained in Preparation Example 10 or 11.The results are shown in Table 9.

Examples 13 and 14

Adhesion Test of Film of PFA having Hydroxyl to Glass

Adhesion test of PFA having hydroxyl to Pyrex glass plate of 30×20×5 mmwas carried out in the manner mentioned below.

Further hot water resistance test and methanol dipping test of thelaminated article after the adhesion were carried out. The results areshown in Table 10.

Production of Test Piece for Tensile Shear Test

FIG. 5 is a diagrammatic perspective view of a test piece for tensileshear test. As shown in Table 5, the PFA film having hydroxyl as anadhesive layer 3 which was obtained in Preparation Example 10 or 11(length f of 10 m, width g of 20 mm, thickness h of 0.1 mm) was putbetween the Pyrex glass sheets 6 (length i of 30 m, width g of 20 mm,thickness j of 5 mm), and a load of 3 kg was applied, followed byallowing to stand at 350° C. for 30 minutes in an electric oven to givea test piece. A thickness of the adhesive layer 3 was adjusted to 0.1 mmwith a spacer.

Adhesive Strength

FIG. 6 is a diagrammatic perspective view of a test device to be usedfor measuring adhesive strength by tensile shearing method. As shown inFIG. 6, the test piece 7 obtained as mentioned above and test jigs 8matching the shape of the test piece were set on TENSILON UniversalTester 9 available from Orientec Corporation, and then the tensileshearing test was carried out at a cross head speed of 20 mm/min. Theresults of the measurement are shown by maximum adhesive strength(kgf/cm²).

Hot Water Resistance Test

The test piece obtained as mentioned above was dipped in 50° C. hotwater to check to see adhesion after a lapse of 6 hours and measureadhesive strength (kgf/cm²) after a lapse of 72 hours.

Methanol Dipping Test

The test piece obtained as mentioned above was dipped in methanol ofroom temperature to check to see adhesion.

Comparative Example 9

Adhesion of Film of PFA having No Functional Group to Glass

Production of a test piece and various tests were carried out in thesame manner as in Example 13 except that the PFA film having nofunctional group and obtained in Preparation Example 12 was used insteadof the PFA film having hydroxyl and obtained in Preparation Example 10or 11. The results are shown in Table 10.

Example 15

Tests for Adhesion and Post-processability after Lamination of PFA Filmhaving Hydroxyl to Stainless Steel

A laminated test plate was produced in the manner mentioned below byusing a degreased SUS304 stainless steel plate of 150 mm long×70 mmwide×0.5 mm thick as a metal plate. The PFA film having hydroxyl andproduced in Preparation Example 13 and the PFA film having no functionalgroup and produced in Preparation Example 14 were cut to the same sizeas the above-mentioned SUS plate.

Further a polyimide film (Kapton 200-H available from E.I. Du Pont)which was used as a film for separation was cut to the same size asabove.

FIG. 7 is a diagrammatic cross-sectional view of a laminated test plate.As shown in FIG. 7, the PFA film 12 having hydroxyl, the PFA film 13having no functional group and the polyimide film 14 were put betweenthe two SUS plates 11, and then set on a press machine preset at 350°C., followed by preheating (20 minutes) and then pressing at 50 kg/cm²for one minute to give a laminated test plate.

After cooling, when the SUS plate 11 contacting the polyimide film 14was removed, the polyimide film was peeled from the interface with thePFA film 13 having no functional group spontaneously.

As a result, a three-layered laminated article having good transparencyand comprising the PFA film 12 having hydroxyl as an adhesive layer, theSUS plate 11 and the PFA film 13 having no functional group wasobtained. FIG. 8 is a diagrammatic cross-sectional view of the obtainedthree-layered laminated article.

Further the surface film of the obtained three-layered laminated articlewas cross-cut with a cutting knife so that a cut depth reached to thesurface of the SUS plate 11, and a hundred pieces of 1 mm squares oflattice pattern was made. A center of the square was pushed out by 5 mmwith Erichsen tester. As a result, the PFA film 12 having hydroxyl wasnot peeled off at all and kept adhered strongly to the SUS plate 11which was a substrate.

The PFA film 12 exhibited strong adhesion to the SUS plate 11.

Comparative Example 10

Tests for Adhesion and Post-Processability after Lamination of PFA Filmhaving No Functional Group to Stainless Steel

A laminated article comprising the SUS plate 11 and the PFA film 13having no functional group was produced in the same manner as in Example15 except that the PFA film having hydroxyl was not used. FIG. 9 is adiagrammatic cross-sectional view of the obtained laminated article.

The film seemed to be adhered, but the PFA film 13 having no functionalgroup could be peeled off from the SUS sheet 11 easily.

Further Erichsen test was carried out in the same manner as in Example15, and 60 pieces among 100 cross-cut squares were peeled off from thecut line.

Example 16

Adhesion Test of PFA Film having Hydroxyl and Polyimide Film

The PFA film 12 having hydroxyl and obtained in Preparation Example 13,the PFA film 13 having no functional group and obtained in PreparationExample 14 and the polyimide film 14 were cut to the same size as inExample 15, and put between the two SUS plates 11, followed by heatingwith a press machine in the same manner as in Example 15 to give alaminated test plate. FIG. 10 shows a diagrammatic cross-sectional viewof the obtained laminated test plate. Then after cooling, the SUS plate11 was removed to obtain a laminated article. FIG. 11 is a diagrammaticcross-sectional view of the obtained laminated article. Further thelaminated article was cut to a width of 25 mm.

Subsequently FIG. 12 is a diagrammatic cross-sectional view of theabove-mentioned laminated article to be subjected to T-type peelingtest. In FIG. 12, a part of interface between the polyimide film 14 andthe PFA film 12 having hydroxyl was peeled, and the T-type peeling testby peeling in the direction of an arrow shown in FIG. 12 was carried outin the same manner as in Example 1. The adhesive strength was 4.0 kgf/25mm as an average value of peel according to area method.

Comparative Example 11

Adhesion Test of PFA Film having No Functional Group and Polyimide Film

FIG. 13 is a diagrammatic cross-sectional view of a laminated article tobe subjected to T-type peeling test in the same manner as in Example 1.In FIG. 13, a part of interface between the polyimide film 14 and thePFA film 13 having no functional group of the 25 mm wide laminatedarticle obtained in Example 16 was peeled, and the T-type peeling testby peeling in the direction of an arrow shown in FIG. 13 was carried outin the same manner as in Example 16, but no adhesive property wasexhibited.

Comparative Example 12

Heat Resistance of Fluorine-containing Polymer Prepared by UsingNon-fluorine-containing Monomer having Functional Group

A thermal decomposition temperature of the fluorine-containing polymerobtained in Preparation Example 9 was measured through TGA analysis, and1% thermal decomposition temperature was 220° C. From that, it is seenthat the fluorine-containing polymer as prepared in Preparation Example9 by using a non-fluorine-containing monomer having functional group haslow heat resistance.

Further the fluorine-containing polymer prepared in Preparation Example9 was dissolved in butyl acetate in a concentration of 10% by weight.

To the aluminum plate pre-treated in the same manner as in Example 9 wasapplied the butyl acetate solution of fluorine-containing polymer ofPreparation Example 9 by an air spray so that a coating thickness wouldbecome about 10 μm, followed by infrared-drying at 90° C. for 10minutes.

On the coating film 16 of the fluorine-containing polymer prepared byusing a non-fluorine-containing monomer having functional group wereplaced in order the PFA film 13 having no functional group and preparedin Preparation Example 14, the polyimide film 14 for separation (same asin Example 15) and the aluminum plate 15, followed by heating andpressing at 350° C. with a press machine in the same manner as inExample 15 to give a laminated test plate. A diagrammaticcross-sectional view of the obtained laminated test plate is shown inFIG. 14.

After cooling the laminated test plate, the aluminum plate 15 contactingthe polyimide film 14 and the polyimide film 14 were removed to give alaminated article.

The obtained laminated article was colored yellow-brown, and foaming andpeeling occurred between the PFA film 13 and the aluminum plate 15. Thusa uniform transparent laminated article could not be obtained.

TABLE 9 Ex. 9 Ex. 10 Com. Ex. 6 Ex. 11 Com. Ex. 7 Ex. 12 Com. Ex. 8 Kindof fluorine- Prep. Ex. 10 Prep. Ex. 11 Prep. Ex. 12 Prep. Ex. 10 Prep.Ex. 12 Prep. Ex. 10 Prep. Ex. 12 containing adhesive Kind of metal plateChromate- Chromate- Chromate- Pure Pure Dull- Dull- treated treatedtreated aluminum aluminum finished finished aluminum aluminum aluminumsteel sheet steel sheet Maximum peeling 15.4 11.3 1.8 9.5 1.5 22.4 2.0strength (kgf/25 mm) Minimum peeling  7.2  2.1 0.18 2.5 0.15 12.4 0.20strength (kgf/25 mm)

TABLE 10 Ex. 13 Ex. 14 Com. Ex. 9 Kind of fluorine- Prep. Ex. 10 Prep.Ex. 11 Prep. Ex. 12 containing adhesive Kind of substrate Pyrex glassPyrex glass Pyrex glass Adhesive strength 83 or more 83 or more 59(kgf/cm²) Breaking of Breaking of Peeling glass glass Hot water Adhesionwas Adhesion was Spontaneous resistance (50° C.) maintained, maintained.peeing 6 hours after Adhesive strength 63 10 — (kgf/cm²) 72 hours afterMethanol dip test Adhesion was — Spontaneous (room temperature)maintained. peeing 24 hours 72 hours Adhesion was — — maintained.

Examples 17 and 18

Non-stickiness test was carried out through the method mentioned belowby using, as a test plate, the plate electrostatically coated with thePFA powder coating composition having hydroxyl of Example 8 (Example 17)and the extruded film of PFA having hydroxyl of Preparation Example 13(Example 18). The results are shown in Table 11.

Non-stickiness Test

Measurement was made at 23° C.±2° C. FIG. 15 is a diagrammaticperspective view of a test piece used for non-stickiness test. The testplate 17 has a length of not less than 150 mm and stains on the surfacethereof was wiped off with acetone. First, a 18 mm wide adhesive tape 18(JIS Z 1522) was cut to a length of 300 mm and only a 150 mm longportion k was put on the test plate 17. Then the tape 18 was scrubbedfor bonding by using an eraser of JIS S 6050 to obtain an adheredportion 19. To the remaining 150 mm long portion is adhered a paper (notillustrated) to make handling of the tape easy. After the bonding, thetape was allowed to stand for about 20 minutes so that the tape 18 wasfitted more to the test plate 17. The tape 18 was peeled up to a width mof 25 mm from the end of the test plate 17, and the test plate 17 wasmounted on a lower chuck device of a tension tester. The end of thepeeled tape 18 was folded by 180 degree, and was fitted to an upperchuck device so that the tape 18 was peeled straight. A force whichpeeled the tape 18 from the test plate 17 with the tester was measuredat a stretching speed of 20 mm/minute. The force was an average of thevalues measured when the tape 18 was peeled smooth. The results areshown in Table 11.

Comparative Examples 15 and 16

Non-stickiness Test of Film of PFA having No Functional Group

Non-stickiness test was carried out in the same manner as in Example 17by using an extruded film of PFA having no functional group and obtainedin Preparation Example 14 (Comparative Example 15) and non-coated glassplate (Comparative Example 16). The results are shown in Table 11.

TABLE 11 Ex. 17 Ex. 18 Com. Ex. 15 Com. Ex. 16 Ex. 8 Prep. Ex. 13 Prep.Ex. 14 — Test sample Plate coated PFA film PFA film Glass plate with PFAhaving having no powder hydroxyl functional coating group compositionhaving hydroxyl Non-sticking 240 235 230 300 property (gf/18 mm)

From Table 11, it was seen that PFA having OH group also has the sameexcellent non-sticking property as PFA having no functional group.

Example 19

Heat Resistance of Adhesion of Plate Coated with PFA Powder CoatingComposition having Hydroxyl

(1) Production of Plate Coated with a Powder Coating Composition

An aluminum plate pre-treated in the same manner as in Example 7 wascoated with a powder coating composition of PFA having hydroxyl andprepared in Preparation Example 7 at room temperature at a voltage of 40kV by electrostatic coating by using an electrostatic powder coatingmachine (the same machine as in Example 8). The coated aluminum platewas sintered at 330° C. for 15 minutes to give a coating film. On theobtained coating film was applied a powder coating composition of PFAhaving no functional group (NEOFLON PFA Powder Coating CompositionACX-31 available from DAIKIN INDUSTRIES, LTD) by electrostatic coatingin the same manner as above, followed by sintering at 380° C. for 20minutes to give a transparent coating film having a total thickness of159 μm.

(2) Measurement of Adhesive Strength

FIG. 16 is a diagrammatic perspective view of an aluminum plate having acoating film obtained in (1) of Example 19. As shown in FIG. 16, thecoating film 20 obtained in (1) above was cut with a cutter at intervalsof a width n (10 mm) until the cutter reached the surface of thesubstrate, and one end of each cut strip of the coating film 20 waspeeled. Thus a coated sample was obtained for measuring adhesivestrength. FIG. 17 is a diagrammatic perspective view of the coatedsample for measuring adhesive strength.

As shown in FIG. 17, the coating film 20 was pulled up at an angle of 90degrees to the aluminum plate 21 and peeling strength was measured. Themeasurement was carried out at room temperature at a cross head speed of50 mm/min by using TENSILON Universal Tester (the same one as in Example7), and an average value of peel according to area method was assumed tobe adhesive strength. The results are shown in Table 12.

(3) Measurement of Heat Resistance of Adhesion

A plate coated with a powder coating composition was produced separatelyin the same manner as in above (1), and put in a hot air dryer set at300° C. After the lapse of 200 hours and 500 hours, the coated plate wastaken out of the dryer. After the respective lapse of time, the coatedplate was cooled to room temperature, and test sample was made andadhesive strength was measured in the same manner as in the above (2).The results are shown in Table 12.

Comparative Example 17

Heat Resistance of Adhesion of Plate Coated with Powder CoatingComposition and having a Primer as an Adhesive Layer

(1) Coating of Primer

An aluminum plate pre-treated in the same manner as in Example 7 wascoated with a heat resisting primer for a fluorine-containing resincoating composition (POLYFLON TFE Enamel EK1959DGN available from DAIKININDUSTRIES, LTD.) by spraying so that the coating thickness would becomeabout 10 μm, followed by sintering at 100° C. for 10 minutes.

(2) Production of Plate Coated with Powder Coating Composition

On the primer-coated plate of above (1) was applied only a PFA powdercoating composition having no functional group (the same one as inExample 19) by electrostatic coating in the same manner as in (1) ofExample 19, followed by sintering at 380° C. for 20 minutes to give acoating thickness of 126 μm including the primer layer.

(3) Measurement of Adhesive Strength

The same procedures as in (2) of Example 19 were repeated. The resultsare shown in Table 12.

(4) Measurement of Heat Resistance of Adhesion

The same procedures as in (3) of Example 19 were repeated. The resultsare shown in Table 12.

Examples 20 and 21

Heat Resistance of Adhesion of Plate Coated with PFA Powder CoatingComposition having Hydroxyl

Plates coated with a powder coating composition were made and adhesivestrength and heat resistance of adhesion were measured in the samemanner as in Example 19 except that instead of the aluminum plate, aSUS430 steel plate pre-treated like the aluminum plate (Example 20) anda galvanized steel plate subjected to only degreasing (Example 21) wereused. The results are shown in Table 12.

Comparative Examples 18 and 19

Heat Resistance of Adhesion of Plate Coated with Powder CoatingComposition and having a Primer as an Adhesive Layer

Plates coated with a powder coating composition were made and adhesivestrength and heat resistance of adhesion were measured in the samemanner as in Comparative Example 17 except that instead of the aluminumplate, a SUS430 steel plate pre-treated like the aluminum plate(Comparative Example 18) and a galvanized steel plate subjected to onlydegreasing (Comparative Example 19) were used. The results are shown inTable 12.

TABLE 12 Ex. 19 Ex. 20 Ex. 21 Com. Ex. 17 Com. Ex. 18 Com. Ex. 19Laminated article Appearance Transparent Transparent Transparent BrownBrown Brown coating film coating film coating film Substrate AluminumSUS430 Galvanized steel Aluminum SUS430 Galvanized steel plate plateSurface layer Film of PFA Film of PFA Film of PFA Film of PFA Film ofPFA Film of PFA powder coating powder coating powder coating powdercoating powder coating powder coating composition compositioncomposition composition composition composition having no OH having noOH having no OH having no OH having no OH having no OH group 1) group 1)group 1) group 1) group 1) group 1) Adhesive layer Film of PFA Film ofPFA Film of PFA Primer for Primer for Primer for powder coating powdercoating powder coating fluorine-coating fluorine-coatingfluorine-coating composition composition composition resin coating 3)resin coating 3) resin coating 3) having OH having OH having OH group 2)group 2) group 2) Coating 140-180 110-140 150-170 120-140 100-120170-200 thickness (μm) Initial adhesive 1.7 1.6 not less than 2.0 2.02.0 0.9 strength (breakage of (kgf/cm) coating film) Heat resistance ofadhesion Adhesive not less than 1.2 not less than 1.5 0.95 0.1 0.7strength at 1.6 (breakage (breakage of 300° C. after of coating film)coating film) 200 hours (kgf/cm) Adhesive not less than 1.1 1.0 0.2 notmore than 0.1 0.4 strength at 1.6 (breakage 300° C. after of coatingfilm) 500 hours (kgf/cm) 1) NEOFLON Powder Coating Composition ACX-31available from DAIKIN INDUSTRIES, LTD. 2) Powder coating compositionobtained in Reference Example 7 3) POLYFLON TFE Enamel EK1959DGNavailable from DAIKIN INDUSTRIES, LTD.

Example 22

Heat Resistance of Adhesion of Laminated Plate of PFA having Hydroxyl

(1) Production of Laminated Plate

An aluminum plate pre-treated in the same manner as in Example 7 wasused as a substrate. A PFA film having hydroxyl and obtained inPreparation Example 13 (thickness 100 μm), a PFA film having nofunctional group (NEOFLON PFA Film AF-0100 available from DAIKININDUSTRIES, LTD.) (thickness 100 μm) and a polyimide film for separation(the same one as in Example 15) were cut to the same size as thesubstrate.

FIG. 18 is a diagrammatic cross-sectional view of a laminated testplate. As shown in FIG. 18, the above-mentioned hydroxyl-containing PFAfilm 23, PFA film 24 having no functional group and polyimide film 25were inserted between the two aluminum plates 22 (one is a substrate),and set on a press machine preset at 350° C., followed by preheating(for 20 minutes) and then pressing at 50 kgf/cm² for one minute. Aftercooling, the polyimide film 25 and aluminum plate 22 contacting thepolyimide film 25 were removed to give a three-layered laminated articlecomprising the hydroxyl-containing PFA film 23 as an adhesive layer,aluminum plate 22 and PFA film 24. FIG. 19 is a diagrammaticcross-sectional view of the obtained three-layered laminated article.

(2) Adhesive Strength

A test sample for measuring adhesive strength was produced by using thelaminated plate (three-layered laminated article) obtained in above (1)instead of the plate coated with a powder coating composition andobtained in (1) of Example 19, and cutting at intervals of a width of 10mm in the same manner as in (2) of Example 19 and peeling one end ofeach strip-like film from an interface between the aluminum plate andthe hydroxyl-containing PFA film layer. The adhesive strength wasmeasured by pulling up the peeled film at an angle of 90 degrees in thesame manner as in (2) of Example 19. The results are shown in Table 13.

(3) Measurement of Heat Resistance of Adhesion

Another laminated plate of above (1) was produced separately, andmeasurement was made by using the produced laminated plate in the samemanner as in (3) of Example 19. The results are shown in Table 13.

Examples 23 and 24

Heat Resistance of Adhesion of Hydroxyl-containing PFA Laminated Plate

Production of laminated plates and measurements of adhesive strength andheat resistance of adhesion were carried out in the same manner as inExample 22 except that instead of the aluminum plate, a SUS430 steelplate surface-treated like the aluminum plate (Example 23) and agalvanized steel plate subjected to only degreasing (Example 24) wereused. The results are shown in Table 13.

Comparative Example 20

Heat Resistance of Adhesion of Laminated Plate Produced by UsingSurface-treated Fluorine-containing Resin Film

(1) Surface-treating of Fluorine-containing Resin Film

One surface of a PFA film having no functional group (NEOFLON PFA FilmAF-0100 available from DAIKIN INDUSTRIES, LTD.) (thickness 100 μm) wassurface-treated with TETRAETCH A (available from Kabushiki KaishaJyunkosha) by the method mentioned below. One surface of the PFA film(adhering surface) was wiped with acetone, and after drying, the wipedsurface was coated with a solution of TETRAETCH A. After the TETRAETCH Asolution was allowed to stand on the film for about 20 seconds, the filmwas washed with methanol and pure water and then dried. The treatedsurface turned brown. Further according to testing method of wettabilityof film described in JIS K-6768, wettability of the treated surface wasdetermined by using a standard test solution of 40 dyn/cm. It wasrecognized that the surface was uniformly wet and had been treatedsufficiently. Water contact angle of the treated surface was 61 degrees(110 degrees before treatment).

(2) Production of Laminated Plate

Two-liquid mixing type heat resisting epoxy adhesive (HITEMP HT-100Lavailable from Kabushiki Kaisha Konishi) was coated on an aluminum platepretreated in the same manner as in Example 7. The surface-treated PFAfilm of above (1) was cut to the same size as the substrate, and itstreated surface was brought into close contact to the adhesive layer ofthe substrate. After heating at 120° C. for one hour, sintering wascarried out at 180° C. for 20 hours for curing and adhering the film tothe substrate.

(3) Measurement of Adhesive Strength

A test sample for measuring adhesive strength was produced in the samemanner as in (2) of Example 22 by using the laminated plate obtained inabove (2) instead of the laminated plate obtained in Example 22, andcutting at intervals of a width of 10 mm and peeling one end of eachstrip-like film from an interface between the PFA film and the adhesivelayer. The adhesive strength was measured in the same manner as in (2)of Example 19 by pulling up the peeled film at an angle of 90 degrees tothe substrate. The results are shown in Table 13.

(4) Measurement of Heat Resistance of Adhesion

Another laminated plate of above (2) was produced, and by using it,measurement was made in the same manner as in (3) of Example 19. Theresults are shown in Table 13.

Comparative Example 21 and 22

Heat Resistance of Adhesion of Laminated Article Produced by UsingSurface-treated Fluorine-containing Resin Film

Surface-treating of a fluorine-containing resin film, production oflaminated plates and measurements of adhesive strength and heatresistance of adhesion were carried out in the same manner as inComparative Example 20 except that instead of the aluminum plate, aSUS430 steel plate surface-treated like the aluminum plate (ComparativeExample 21) and a galvanized steel plate subjected to only degreasing(Comparative Example 22) were used. The results are shown in Table 13.

Comparative Example 23

Heat Resistance of Adhesion of Laminated Article Produced by UsingSurface-treated Film

(1) surface Treatment of Fluorine-containing Resin Film

A surface-treated FEP film (NEOFLON FEP Film NF-0100B1 available fromDAIKIN INDUSTRIES, LTD., one side is surface-treated) (thickness 100 μm)was used instead of the PFA film of (1) of Comparative Example 20surface-treated with TETRAETCH.

(2) Production of Laminated Plate

An epoxy adhesive was coated on a pre-treated aluminum plate and asurface-treated film was laminated on the coated aluminum plate in thesame manner as in (2) of Comparative Example 20 except that thesurface-treated FEP film of above (1) was used instead of the PFA filmsurface-treated with TETRAETCH.

(3) Measurement of Adhesive Strength

Production of a test sample and measurement of adhesive strength werecarried out in the same manner as in Comparative Example 20 except thatthe laminated plate obtained in above (2) was used instead of thelaminated plate which was produced by using a PFA film treated withTETRAETCH in (2) of Comparative Example 20.

(4) Measurement of Heat Resistance of Adhesion

Another laminated plate of above (2) was produced, and by using it,measurement was carried out in the same manner as in (3) of Example 19.The results are shown in Table 13.

Comparative Example 24 and 25

Heat Resistance of Adhesion of Laminated Plate Produced by UsingSurface-treated Fluorine-containing Resin Film

Production of laminated plates, and measurements of adhesive strengthand heat resistance of adhesion were carried out in the same manner asin Comparative Example 23 except that instead of the aluminum plate, aSUS430 steel plate surface-treated like the aluminum plate (ComparativeExample 24) and a galvanized steel plate subjected to only degreasing(Comparative Example 25) were used. The results are shown in Table 13.

TABLE 13 Ex. 22 Ex. 23 Ex. 24 Com. Ex. 20 Com. Ex. 21 Com. Ex. 22 Com.Ex. 23 Com. Ex. 24 Com. Ex. 25 Laminated article Appearance TransparentTransparent Transparent Brown Brown Brown Brown Brown Brown coating filmcoating film coating film Substrate Aluminum SUS430 Galvanized AluminumSUS430 Galvanized Aluminum SUS430 Galvanized steel plate steel platesteel plate Surface layer Film of PFA Film of PFA Film of PFA PFA filmPFA film PFA film Surface- Surface- Surface- having no having no havingno surface-treated surface-treated surface-treated treated FEP treatedFEP treated FEP OH group 1) OH group 1) OH group 1) with TETRA_ withTETRA- with TETRA- film 4) film 4) film 4) ETCH ETCH ETCH Adhesive PFAfilm PFA film PFA film Heat resisting Heat resisting Heat resisting Heatresis- Heat resis- Heat resis- layer having OH having OH having OH epoxyadhesive epoxy adhesive epoxy adhesive tive epoxy tive epoxy tive epoxygroup 2) group 2) group 2) 3) 3) 3) adhesive 3) adhesive 3) adhesive 3)Coating 180-220 170-200 200-230 150-190 160-190 170-190 130-160 160-180160-180 thickness (μm) Initial adhe- 2.1 2.5 2.2 1.6 1.0 1.6 1.5 1.5 1.5sive strength (kgf/cm) Heat re- sistance of adhesion Adhesive not lessthan 2.2 not less than Spontaneous Spontaneous Spontaneous SpontaneousSpontaneous Spontaneous strength at 2.0 (break- 2.0 (break- peelingpeeling peeling peeling peeling peeling 300° C. after age of film) ageof film) (peeling at (peeling at (peeling at (peeling at (peeling at(peeling at 200 hours substrate side) substrate side) substrate side)substrate substrate substrate (kgf/cm) side) side) side) Adhesive notless than 2.2 not less than Spontaneous Spontaneous SpontaneousSpontaneous Spontaneous Spontaneous strength at 2.0 (break- 2.0 (break-peeling peeling peeling peeling peeling peeling 300° C. after age offilm) age of film) (peeling at (peeling at (peeling at (peeling at(peeling at (peeling at 500 hours substrate side) substrate side)substrate side) substrate substrate substrate (kgf/cm) side) side)side) 1) NEOFLON PFA Film AF-0100 available from DAIKIN INDUSTRIES, LTD.2) Film obtained in Preparation Example 13 3) HITEMP HT-100L availablefrom Kabushiki Kaisha Konishi 4) NEOFLON FEP Film NF-0100B1 availablefrom DAIKIN INDUSTRIES, LTD.

According to the present invention, it is possible to obtain a compositematerial for cooking apparatuses which is produced by applying, to asubstrate, a material comprising a fluorine-containing polymer havingexcellent adhesive property, without necessitating complicated steps.Further according to the present invention, it is possible to obtain acomposite material for cooking apparatuses which is excellent in heatresistance, non-sticking property, stain-proofing property, water- andoil-repelling property, stain removing property, chemical resistance,rust-preventive property, antibacterial property, resistance to energyray and friction property.

What is claimed is:
 1. A method for endowing a cooking apparatus withheat resistance of adhesion which comprises applying, between asubstrate and a surface layer, a material comprising afluorine-containing ethylenic polymer having functional group andprepared by copolymerizing; (a) 0.05 to 30% by mole of at least one offluorine-containing ethylenic monomers having at least one functionalgroup selected from the group consisting of hydroxyl, carboxyl, acarboxylic salt group, a carboxylic ester group and epoxy, and (b) 70 to99.95% by mole or at least one of fluorine-containing ethylenic monomershaving no functional group mentioned above; said surface layercomprising a layer of a fluorine-containing ethylenic polymer having nofunctional group.